Hugh Janus

The Airbag Vest (Illustration by Justin Page/)The full-face helmet is only about 50 years old. And not to be too obvious, but before that, not one person ever used one on a motorcycle. Today many riders wouldn’t ride with anything less. Could wearable air bag ­protection in your riding jacket or race suit become the safety standard in the same way? Leading gear companies Dainese and Alpinestars have been working over the course of the past two ­decades to make it so, and motorcyclists have enjoyed the fruit of this rivalry that has created the most ­technologically advanced safety standard to date. The race in earnest began in 1995, when Dainese initiated developmental work on its air bag system—­later named D-Air. Alpinestars arrived at the party in 2001 with its Tech-Air project. Work for both companies began primarily in the regulated and semipredictable space of Grand Prix racing, where each company steadily collected the data used to improve algorithms and the rate of crash detection. By 2009, both Alpinestars and Dainese had fully functioning prototype systems being used by racers in MotoGP. The first race-situation activation of D-Air was triggered at the 2007 Valencia GP by Italian racer Simone Grotzky. Dainese’s Smart Jacket is capable of a single deployment. Following activation, the system must be taken to an official D-Air dealer for maintenance and recharging—the service costs $249.99. (Dainese/)Wearable air bag protection was made publicly available in pre-equipped race-focused suits and expensive jackets by both Alpinestars and Dainese in 2011, although neither system hit the US market until 2015 due to varying standards on electronic devices. But finally, MotoGP-level protection was available for all. The objective of air bag systems is to detect and protect against an injury before any impact has actually occurred—chances are, before you even realize you’re crashing. To be able to do this, the brain of the latest D-Air system, or Intelligent Protection System, uses seven sensors, including three accelerometers, three gyroscopes and a GPS unit. In current systems, Dainese claims the sensors autonomously scan to detect a nascent accident 1,000 times per second. In the event the system determines that a crash is imminent, the system inflates within milliseconds, with the goal of being completely expanded prior to impact. This last point is arguably the most important factor. Weighing in at roughly 4 pounds, the Smart Jacket is lightweight and easily stowable. Versatility is key. (Dainese/)Once triggered, a rush of gas from charged, ­high-pressure cartridges fills areas surrounding the shoulders, chest, ribcage and back on the most advanced systems —a volume as large as 11 liters on the street-based D-Air Road system. And how does this compare to the protection of traditional equipment? Dainese says there is a 90 percent reduction in force transmitted to the body. Or as Alpinestars expresses it for the Tech-Air system: It’s the same level of protection as wearing 18 back protectors in the area covered by the air bag. The next step in air bag development? Leading ­companies have objectives of improving the versatility of systems while making them more affordable. Meet the recently introduced Dainese Smart Jacket and ­Alpinestars Tech-Air 5 systems. Both are slim, ­self-contained systems with the capability of fitting under street jackets, matching brand or not. The only requirement is roughly 2 inches of free space in ­circumference underneath your chosen garment. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. These systems are serious steps in the right direction. What you get is the latest safety technology derived from MotoGP racing, millions of real-world testing miles, and thousands of analyzed air bag deployments—all optimized with algorithms specialized in detecting accidents found in real-world scenarios, even at a standstill. And in the case of the Dainese Smart Jacket, it’s priced at a relatively affordable $699.95. Crash detection is vital to maximum protection. Here, my D-Air Racing suit has activated—notice the inflated shoulders—prior to impact. (Corey J Coulter/)Personally speaking, investing in air bag protection is a no-brainer. At the 2018 season-opening MotoAmerica Supersport race at Road Atlanta, a wicked slide catapulted me to the biggest highside of my racing career, triggering the inflation of my D-Air Racing suit before hitting the tarmac. The injuries? Double sprained ankles and a knock to the head—but zero injuries to my collarbones, chest or shoulders, not even the one with an existing, nagging injury. The air bag protected me in a huge crash and is the reason I was healthy enough to compete at the following race only two weeks later. I’ll never race without an air-bag-equipped suit again. Alpinestars says the air bag will inflate between 20 to 40 milliseconds after a crash has been detected. (Alpinestars/)KTM factory MotoGP racer Pol Espargaro sums it up best: “Once you’ve tried D-Air, it’s something that you can’t do without,” the Spaniard says. “At one time, not wearing a helmet was the norm. Now it’s mandatory to wear one, and you can’t do without one. It’s the same with the air bag.” Yeah, exactly. Source

The 2020 KTM 500 EXC-F is the brand’s leading dual sport model and a highly capable one at that. Proof? It’s hard to deny its credentials, including being named Cycle World’s Best Enduro/Dual Sport five times in the past 10 years. It’s powered by a liquid-cooled, SOHC, 511cc four-stroke engine, and comes fitted with premium components like Brembo brake calipers and WP Xplor suspension. All the pieces needed for a leading dual sport bike. 2020 KTM 500 EXC-F Dyno Chart (Robert Martin/)Ahead of an upcoming dual sport comparison, we ran the 500 EXC-F on our in-house Dynojet 250i dynamometer to determine horsepower and torque measurements. The big-displacement KTM recorded 39.4 hp at 8,100 rpm and 27.7 pound-feet of torque at 5,200 rpm. RELATED: Honda CRF450L vs. KTM 500 EXC-F vs. Husqvarna FE 450 vs. Beta 430 RR-S Source

2020 Honda CRF250RX (Honda /)The Honda CRF250RX is Big Red’s 250cc four-stroke cross-country competition bike. It has many of the same features as its motocross stablemate, the CRF250R, but sees changes like a larger fuel tank, 18-inch rear wheel, kickstand, O-ring chain, and modified suspension settings to extract more off-road performance. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. 2020 Honda CRF250RX Reviews, Comparisons, And Competition After testing the 2019 Honda CRF250RX at the bike’s intro at Cahuilla Creek MX in Anza, California, we logged more than 400 miles of off-road and motocross riding on it and were impressed with its performance. After getting to know its characteristics in stock trim, we added some aftermarket parts to it that improved its worth as an all-around MX and off-road bike. 2020 Honda CRF250RX (Honda /)Some competitors for the 2020 Honda CRF250RX include the 2020 Yamaha YZ250FX and 2020 KTM 250 XC-F. As far as pricing, the CRF250RX costs $8,299, which is $200 less than the YZ250FX and $1,200 less than the 250 XC-F. Honda CRF250RX Updates For 2020 The Honda CRF250RX was first introduced in 2019, but received a slew of changes for 2020 including a new exhaust cam profile, an optimized combustion chamber shape, and the addition of a gear-position sensor. On the exhaust system, the resonator on the header pipe was removed. Also, the bike’s air filter size was increased by 10 percent and the left-side radiator was enlarged. Among other revisions to the transmission and clutch, the CRF250RX received a lighter frame and swingarm, newly shaped footpegs, and the battery was repositioned 28mm lower. Multiple parts of the rear brake were new along with the graphics. 2020 Honda CRF250RX (Honda /)2020 Honda CRF250RX Claimed Specifications Price $8,299 Engine Liquid-cooled DOHC single-cylinder Displacement 249cc Bore x Stroke 79.0 x 50.9mm Horsepower N/A Torque N/A Transmission 5-speed Final Drive Chain Seat Height 37.8 in. Rake 27.4° Trail 4.5 in. Front Suspension 49mm inverted fork, fully adjustable; 12.0-in. travel Rear Suspension Fully adjustable; 12.4-in. travel Front Tire 80/100-21 Rear Tire 110/100-18 Wheelbase 58.5 in. Fuel Capacity 2.25 gal. Claimed Wet Weight 244 lb. Source

2020 Honda Monkey (Honda /)The 2020 Honda Monkey is a true throwback of the original hit from the 1960s. This is a minibike that houses the compact 125cc single-cylinder engine that is also seen on the Grom. Its short wheelbase, low seat height, and small engine displacement will continue to appeal to new riders or those of us who want to harken back to the good old days. 2020 Honda Monkey Reviews, Comparisons, And Competition Because of its Grom base and rich nostalgia, as soon as the 2019 Honda Monkey was unveiled it had already stolen our hearts like a teenage girl and her favorite boy band heartthrob. In fact, Cycle World contributor Peter Jones noted in his first impression of the Monkey that, “The immediate riding impression of today’s Monkey is one of pure, visceral, monstrous fun. It’s a barrel of let’s-do-it-again fun,” he wrote. “It’s a little bike that makes every rider a kid.” Yeah, exactly. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. There are a few competitors within this mini moto space, including the Honda Grom, Honda Super Cub, and Kawasaki Z125, but nothing quite packs the reminiscent punch like the Monkey. 2020 Honda Monkey (Honda /)Honda Monkey Updates For 2020 It will now be available in Pearl Glittering Blue in addition to the Pearl Nebula Red. This small bike comes at a small starting price of just $3,999 or $4,199 with ABS. 2020 Honda Monkey Claimed Specifications Price $3,999 Engine Air-cooled SOHC single-cylinder Displacement 125cc Bore x Stroke 52.4 x 57.9mm Horsepower N/A Torque N/A Transmission 4-speed Final Drive Chain Seat Height 30.6 in. Rake 25.0° Trail 3.2 in. Front Suspension 32mm inverted fork, nonadjustable; 3.9-in. travel Rear Suspension Twin shock; 4.1-in. travel Front Tire 120/80-12 Rear Tire 130/80-12 Wheelbase 45.5 in. Fuel Capacity 1.5 gal. Claimed Wet Weight 232 lb. Source

2020 Honda Grom (Honda/)When a motorcycle can serve the dual purpose of bringing new riders into motorcycling and making veteran riders smile from ear to ear, you know you have a model that will maintain its beloved nature year after year. And such is the Honda Grom. Originally introduced in 2014, this little 125cc bike brought smiles to many of the editors’ faces with the moto shenanigans that it invites. With its unintimidating, approachable power and overall small-bike nimbleness, the Grom continues to be a great around-town runner. 2020 Honda Grom (Honda/)2020 Honda Grom Reviews, Comparisons, And Competition The 2020 Grom’s base MSRP is $3,399 and is contested by the Kawasaki Z125 PRO’s $3,199. Both in engine displacement, approachability, and price, these two can be considered neck and neck. 2020 Honda Grom (Honda/)Honda Grom Updates For 2020 No major changes for 2020. You can continue to choose from either the standard or ABS forms. This upgrade to the rider-aid-equipped version only adds $200 to the standard’s MSRP, though it will cost you a few colors to choose from. The ABS version is only available in Cherry Red whereas the standard is available in Cherry Red, Blue Raspberry, Halloween Orange, and Incredible Green. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. 2020 Honda Grom (Honda/)2020 Honda Grom Claimed Specifications Price $3,399 Engine Air-cooled SOHC single-cylinder Displacement 125cc Bore x Stroke 52.4 x 57.9mm Horsepower N/A Torque N/A Transmission 4-speed Final Drive Chain Seat Height 30.0 in. Rake 25.0° Trail 3.2 in. Front Suspension 31mm inverted fork, nonadjustable; 3.9-in. travel Rear Suspension Single shock; 4.1-in. travel Front Tire 120/70-12 Rear Tire 130/70-12 Wheelbase 47.2 in. Fuel Capacity 1.5 gal. Claimed Wet Weight 229 lb. Source

2020 Honda CRF50F (Honda/)The 2020 Honda CRF50F is the ultimate learning tool for young riders. Its automatic clutch makes one less thing for the little one to manage, but the three gears still allow them to learn the importance of shifting via the shift lever. Don’t want your kid to head off into the hills? The adjustable throttle limiter and keyed ignition are safety features that help you maintain control. Looking for a tricked-out pitbike? The CRF50F serves as one of the original platforms for pitbike racing. Several companies offer hop-up kits for this Honda, including big-bore kits, upgraded suspension, and customized aesthetics. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. 2020 Honda CRF50F Reviews, Comparisons, And Competition The CRF50F does have some competition in the Yamaha PW50 ($1,499) or TT-R50E ($1,699), Suzuki DR-Z50 ($1,749), and KTM 50 SX ($3,849) or 50 SX Mini ($4,349). As you can see the CRF50F’s $1,549 pricing is challenged by the competition as well. Honda CRF50F Updates For 2020 There aren’t any changes for 2020, even the graphics remain unchanged. 2020 Honda CRF50F Claimed Specifications Price $1,549 Engine Air-cooled SOHC single-cylinder Displacement 49cc Bore x Stroke 39.0 x 41.4mm Horsepower N/A Torque N/A Transmission 3-speed w/ automatic clutch Final Drive Chain Seat Height 21.6 in. Rake 25.0° Trail 1.3 in. Front Suspension Inverted telescopic fork; 3.5-in. travel Rear Suspension Single shock; 2.8-in. travel Front Tire 2.50-10 Rear Tire 2.50-10 Wheelbase 36.0 in. Fuel Capacity 0.7 gal. Claimed Wet Weight 110 lb. Source

2020 Husqvarna FC 450 Rockstar Edition (Husqvarna /)Having first hit the market in 2018, the 2020 Husqvarna FC 450 Rockstar Edition is the Austrian manufacturer’s third iteration of the limited-edition machine. The mechanical changes the FC 450 Rockstar Edition receives each year usually serve as a preview of what the following year’s motocross models will come with in terms of updates. The FC 450 Rockstar Edition always features a number of aftermarket components and Husqvarna Technical Accessories such as a factory triple clamp, FMF Factory 4.1 RCT muffler, and a Rekluse clutch cover just to name a few. 2020 Husqvarna FC 450 Rockstar Edition Reviews, Comparisons, And Competition We rode the 2020 Husqvarna FC 450 Rockstar Edition at Glen Helen Raceway in San Bernardino for the introduction of the special-edition machine. Off-Road Editor Andrew Oldar was impressed with the bike’s stronger power delivery and firmer suspension settings in comparison to the standard FC 450 model. “The 2020 FC 450 Rockstar Edition’s updated maps give it a more aggressive power delivery, yet the bike still maintains its easy-to-ride and controllable nature. The bike’s suspension is more of a race setting than what the standard 2020 FC 450 model offered, and is more of a well-rounded setup for a variety of different tracks.” 2020 Husqvarna FC 450 Rockstar Edition (Husqvarna /)There are two other special-edition motocross bikes each year that serve as competition for the 2020 Husqvarna FC 450 Rockstar Edition including the 2020 KTM 450 SX-F Factory Edition and the 2020 Honda CRF450RWE. At $11,199, the FC 450 Rockstar Edition is the most expensive of the three; it’s $100 more than the 450 SX-F Factory Edition and $1,800 pricier than the CRF450RWE. 2020 Husqvarna FC 450 Rockstar Edition (Husqvarna /)Husqvarna FC 450 Rockstar Edition Updates For 2020 For 2020, Husqvarna updated its FC 450 Rockstar Edition with suspension changes and new ECU mapping. The WP Xact air fork has a new oil bypass in the outer tube of the damping leg, a 10mm longer bypass in the air leg, a smaller rebound spacer to increase the air volume in the negative chamber, a new mid-valve damping system, a new adjuster for the rebound on the bottom of the fork, a new elastomer end stop, and a new air piston. The WP Xact shock also received changes in the form of a higher spring rate, a new O-ring in the link piston, and new low-friction linkage seals. 2020 Husqvarna FC 450 Rockstar Edition Claimed Specifications Price: $11,199 Engine: Liquid-cooled SOHC single-cylinder Displacement: 450cc Bore x Stroke: 95.0 x 63.4mm Horsepower: N/A Torque: N/A Transmission: 5-speed Final Drive: Chain Seat Height: 37.4 in. Rake: 26.1° Trail: N/A Front Suspension: 48mm inverted fork, fully adjustable; 12.2-in. travel Rear Suspension: Fully adjustable; 11.8-in. travel Front Tire: 80/100-21 Rear Tire: 120/80-19 Wheelbase: 58.5 in. Fuel Capacity: 1.9 gal. Claimed Wet Weight: 223 lb. Source

Patent drawings show Honda looking at wishbone-style front suspension for future models, like the CB1100. (Japanese Patent Office/)In adopting double-wishbone front suspension for its range-topping Gold Wing in 2018 Honda embraced the same thinking that pushed the likes of Norman Hossack and John Britten into ditching telescopic forks, and now it looks like the company has ideas to spread the technology further across the range. The firm has filed patent applications in Japan for wishbone-style front suspension on bikes at extreme ends of its range. One shows the system adapted for an across-the-frame four-cylinder—in this case the CB1100—while the other reveals how the design can be modified to fit the C125 Super Cub scooter. Unlike the Gold Wing, the CB1100 relies on a retro-heavy overall design that favors a conventional fork arrangement, making a wishbone arrangement challenging. (Japanese Patent Office/)The Wishbone-Equipped CB1100 Honda experimented with a variety of alternative front suspension systems while developing the latest Gold Wing before settling on a Hossack/Fior-style arrangement that’s not a million miles from BMW’s Duolever system, as used on the K 1600. The idea was always to combat the braking dive of the heavy Gold Wing, to reduce the strain on the headstock section of the chassis and to ensure a consistent wheelbase throughout the suspension travel, in turn allowing a shorter wheelbase to be used. And since the idea worked on the Wing, it makes sense the firm is looking at whether other bikes might benefit. The CB’s engine position required Honda to rethink the lower wishbone’s front pivot point; the engineers moved it forward. (Japanese Patent Office/)The CB1100 might not be an obvious candidate for wishbone suspension. As the most overtly retro offering in Honda’s range—complete with air-cooled engine and twin rear shocks—its styling and engineering are heavily biased toward a conventional telescopic front suspension system. But perhaps that’s why Honda chose that bike to experiment with wishbone suspension; if it can work on the CB1100, it can probably be made to work almost anywhere. Although the basic layout is similar to the Gold Wing’s, there are significant changes for the wishbone CB1100. Most importantly, the engine’s position doesn’t allow the lower wishbone’s rear pivot to be mounted as far back as on the Wing. On the Gold Wing, the lower wishbone is mounted further back than the upper one, allowing the lower link to be significantly longer than the upper. To achieve the same ratio of link length, Honda had to rethink the idea for the inline-four CB1100. RELATED: 2018 Honda Gold Wing Tour vs. BMW K1600B Grand America With the engine getting in the way of having the lower wishbone’s rear pivot mounted a long way back, Honda’s solution is to move the lower wishbone’s front pivot point forward. That keeps the lower wishbone long relative to the upper one—around twice the length—but means it must reach around the upright above the front wheel bracket extending from the front. The CB’s bars were also a challenge, as they are positioned directly on top of the fork. Honda’s solution was to use a two-part linkage. (Japanese Patent Office/)Another change compared to the Gold Wing is the steering system. On the Wing, the bars are mounted much further back, which means Honda could use a simple linkage running parallel with the upper wishbone to connect the bars to the fork. On the CB1100, with the bars mounted directly above the top of the fork, that’s not possible so the firm has opted to use a two-part linkage that concertinas as the suspension compresses. This is the same solution used by BMW for the similar Duolever front end on the K 1600. RELATED: Honda Adds Super Cub And XR650L To 2020 Lineup As with all wishbone-style front suspension systems, another advantage is that a single coilover shock can be used to do the springing and damping, which puts the CB1100 seen here in the odd position of having a single front shock and two rear ones—the reverse of a typical modern motorcycle. At the opposite end of Honda’s range is the Super Cub, a smaller and lighter model and also an unlikely candidate for a wishbone setup. (American Honda Motor Co./)The Wishbone-Equipped C125 Super Cub While the theoretical advantages of a wishbone front end remain the same regardless of the type of bike, putting the system on the C125 is testing it at the very opposite end of Honda’s range compared to the Gold Wing currently using the idea. Not only is the C125 a much smaller machine, but it’s far lighter and features a completely different chassis design with different materials and a different engine layout. That’s probably why it’s been used as another guinea pig for Honda’s experimentation. In fact, the latest Super Cub is a late adopter of the telescopic fork; earlier iterations like the C50 and C90 used leading-link front suspension instead, but the Hossack-style wishbone setup seen here is a complete departure for the bike. With a low-mounted single-cylinder engine it doesn’t have the same geometry problem as the CB1100 when it comes to where the rear wishbone pivots are attached. However, here Honda has opted for equal-length wishbones top and bottom. The argument for using the wishbone front end on the C125 is that it gives more freedom for the position of the bars in relation to the front wheel, allowing a small bike to have a more spacious riding position than if it was fitted with conventional forks. With the Super Cub’s more favorable geometry, Honda could use the same length wishbone both top and bottom. (Japanese Patent Office/)Will these ideas lead to production bikes? Just because a firm files patent applications for an idea doesn’t mean it will make it to production. However, it is a clear indication of what the company’s R&D department is working on. In the case of the Gold Wing, Honda filed multiple patent applications for several different alternative front suspension systems before settling on the Hossack-style design that reached production. What was clear was that the firm wanted to get away from the limitations of telescopic forks, and it tested several solutions before choosing one that worked best. We’ll keep an eye on Honda’s patents over the coming months to see if the firm continues to develop this idea. A wishbone setup would be a complete departure for the C125, but it would allow for greater freedom in handlebar positioning. (Japanese Patent Office/)Interestingly, as Honda moves toward alternative front suspension, BMW—the firm that pursued odd front ends for years with the Telelever and Duolever setups—has moved back toward telescopic forks. These days the majority of BMWs use telescopic forks, with just the Duolever K 1600 and Telelever R 1250 GS staying with alternative front ends. Source

2020 Harley-Davidson Fat Bob (Harley-Davidson /)We became big fans of the Fat Bob 114 right from the launch in 2018 because it offered seemingly impossible dynamics from a chunky-tired chassis and big-bore engine. Despite its unique looks defined by the signature horizontal LED headlight and 2-into-1-into-2 exhaust (H-D designers say they built this bike “for the zombie apocalypse”) the muscular, Softail-based cruiser represents a seismic shift from The Motor Company’s traditional V-twin profile. But if the Fat Bob 114 stretches The Motor Company’s styling DNA the most, it also pushes the boundaries of expected performance, with a steep 28-degree rake, dual disc brakes, and a solidly mounted 114ci Milwaukee-Eight V-twin engine giving it a combination of power and agility you don’t find on most cruisers. 2020 Harley-Davidson Fat Bob (Harley-Davidson /)2020 Harley-Davidson Fat Bob 114 Reviews, Comparisons, And Competition The Fat Bob 114 was so much fun to ride, we picked it as Cycle World’s Best Cruiser of 2018. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. The last time we ran it on the Cycle World dyno, the portly Softail made 82.3 hp and 111.39 pound-feet of torque, so it matches well against other beefy models in the musclebike category, such as the Ducati Diavel, Yamaha’s evergreen VMAX, and Triumph’s new Rocket 3, due similar category positioning and intent. We matched up a couple of those models in a power cruiser shootout last year. 2020 Harley-Davidson Fat Bob (Harley-Davidson /)Harley-Davidson Fat Bob 114 Updates For 2020 When it was first launched, the Fat Bob was available in both 107 and 114ci engine options, but for 2020 it only rolls with the Milwaukee-Eight 114, and ABS and security comes standard.There are new color options and pricing as well. Manufacturer Claimed Specifications Price $18,799–$19,749 Engine Air-/oil-cooled, OHV V-twin; 4 valves/cyl. Displacement 1,868cc Bore x Stroke 102.0mm,x 114.0mm Horsepower N/A Torque 118 lb.-ft. @ 3,500 rpm Transmission 6-speed Final Drive Belt Seat Height 27.7 in. Rake 28.0° Trail 5.2 in. Front Suspension 43mm inverted fork; 5.1-in. travel Rear Suspension Preload adjustable; 4.4-in. travel Front Tire 150/80-16 Rear Tire 180/70-16 Wheelbase 63.6 in. Fuel Capacity 3.6 gal. Claimed Wet Weight 676 lb. Source

2020 Honda CRF150R (Honda/)The Honda CRF150R and CRF150R Expert were introduced in 2007. The 150 four-stroke machines replaced Big Red’s long-standing CR85R and CR85R Expert two-stroke models that year and have remained as the Japanese manufacturer’s two youth motocross bikes ever since. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. 2020 Honda CRF150R Reviews, Comparisons, And Competition Some competitors of the 2020 Honda CRF150R include the Suzuki RM85, Yamaha YZ85, KTM 85 SX, Husqvarna TC 85, Kawasaki KX85, and TM MX 85. The 2020 Honda CRF150R has a suggested retail price of $5,099, while the CRF150R Expert is $5,299. 2019 Honda CRF150R Expert (Honda/)Honda CRF150R Updates For 2020 The Honda CRF150R did not receive any changes for 2020. In addition to the CRF150R, which has a 17-inch front wheel and a 14-inch rear wheel, Honda also offers the CRF150R Expert, which has a 19-inch front wheel, 16-inch rear wheel, a taller seat height, and a longer wheelbase–offering an ideal steppingstone to full-size motocrossers. 2020 Honda CRF150R Claimed Specifications Price $5,099 Engine Liquid-cooled SOHC single-cylinder Displacement 149cc Bore x Stroke 66.0mm x 43.7mm Horsepower N/A Torque N/A Transmission 5-speed Final Drive Chain Seat Height 32.8 in. Rake 27° Trail 3.1 in. Front Suspension 37mm inverted fork, fully adjustable; 10.8-in. travel Rear Suspension Fully adjustable; 10.7-in. travel Front Tire 70/100-17 Rear Tire 90/100-14 Wheelbase 49.6 in. Fuel Capacity 1.1 gal. Claimed Wet Weight 185 lb. 2020 Honda CRF150R Expert Claimed Specifications Price $5,299 Engine Liquid-cooled SOHC single-cylinder Displacement 149cc Bore x Stroke 66.0mm x 43.7mm Horsepower N/A Torque N/A Transmission 5-speed Final Drive Chain Seat Height 34.1 in. Rake 27.8° Trail 3.8 in. Front Suspension 37mm inverted fork, fully adjustable; 10.8-in. travel Rear Suspension Fully adjustable; 10.7-in. travel Front Tire 70/100-19 Rear Tire 90/100-16 Wheelbase 50.6 in. Fuel Capacity 1.1 gal. Claimed Wet Weight 187 lb. Source

There’s a buzz within Cycle World headquarters lately. The hum of electric motorcycles charging during the workday can be heard in the halls as staff members have plugged into the merits of two-wheeled EV transportation. Whether zapping to and from work or effortlessly whistling about the greater Los Angeles area without so much as pulling a clutch or toeing a shift lever, EV bikes have proven to be a viable mode of urban transportation. Enthusiasm has been recently supercharged with the simultaneous arrival of the 2020 Harley-Davidson LiveWire and Zero SR/F Premium, a pair of preeminent models within the segment and the natural makings of a heads-up comparison. The current crop of EV motorcycles leading the charge—the class benchmark Zero Motorcycles SR/F Premium and Harley-Davidson’s all-new LiveWire. (Jeff Allen /)These full-fledged roadbikes are each endowed with chassis specifications, ergonomics, and styling well in line with a contemporary petrol-powered liter-class sport naked. Both feature comprehensive IMU-based rider aids with lean-sensing traction control, cornering ABS, and have selectable ride modes for Sport, Street, Rain, and Eco that tailor throttle response, peak power output, regenerative braking, and TC sensitivity. Both have a TFT dash display providing a wealth of info to monitor charging status, estimated range, state of charge, ride mode selection, and more. The physical size and load capacity of these bikes facilitates use of a larger lithium-ion battery pack than any EV motorcycle we’ve tested in the past. Each bike’s power pack is encased in an aluminum heat-sink housing, lending a stylistic appearance along with the strength and rigidity to serve as a stressed member of the frame. Zero employs a tubular steel-trellis frame wrapping its 14.4kWh Z-Force battery unit, while Harley’s frame structure is composed of aluminum cast members bolted to its 15.5kWh Rechargeable Energy Storage System (RESS) that join at the steering head. Built for the urban confines, but still capable canyon carvers. The hills of central California exposed the true sporting characteristics of each. (Jeff Allen /)While both are propelled by an interior permanent-magnet brushless AC motor, their powertrain configurations are fundamentally different. Zero’s ZF75-10 motor is a passive air-cooled design mounted with its power shaft horizontally across the frame, using a final-drive pulley attached directly to the motor’s shaft. The Revelation motor of the Harley-Davidson resides beneath the RESS in a longitudinal arrangement, features a liquid-cooling jacket, and employs gear-ratio-reducing spiral-bevel-gear primary drive that transmits torque to its perpendicular countershaft/sprocket arrangement. Measuring power output at the rear wheel on the Cycle World dyno revealed an interesting contrast in engineering approach. Viewing each bike’s peak torque value alone would lead one to surmise that the Zero’s 146.5 pound-feet flat buries the 74.0 pound-feet Harley. The LiveWire’s high-level fit and finish is what you’d expect of an established premium motorcycle manufacturer that’s been building motorcycles for more than a century. (Jeff Allen /)First, note that the LiveWire motor spins beyond 14,000 rpm, while the Zero tails off around 7,000 rpm. Horsepower produced at higher revs mathematically equates to notably less torque than when the same horsepower value is produced at a lower rpm. Comparing the two at a dyno drum speed of 55 mph, we found the Zero produces 80 hp and 120 pound-feet at 3,500 rpm, while the Harley dealt 91 hp and 68 pound-feet at 7,000 rpm. It’s much like your classic gas-powered matchup of a big-inch twin and high-revving inline-four. Harley-Davidson’s role reversal of leveraging revs while the competition leans on low-rpm torque truly is a Revelation. Tipping our scale at 502 pounds ready to ride, the SR/F Premium would also appear to enjoy a power-to-weight advantage on the 544-pound LiveWire. The Harley has 8-percent more energy storage capacity however, justifying the additional pounds that also pencils out at 8.4 percent. Flat-out acceleration on these EV motorcycles is impressive and highly addicting. Beware, however, battery range is highly dependent on riding habits. (Jeff Allen /)Putting rubber to the road at our test facility, the acceleration runs measured with a VBox GPS datalogger provided more surprises. The LiveWire sprinted the quarter-mile in 11.54 seconds with a 110.63-mph trap speed, putting the Zero in its mirrors with a best pass of 11.83 seconds at 116.2 mph. Comparing trap speed is a telling clue the LiveWire accelerates quicker, flexing shorter overall gearing that’s clearly illustrated in the comparative 0–60 mph time. Here the LiveWire’s 3.12-second showing crushes the Zero’s 3.65-second 0–60 time and accounts for the overall ET. The LiveWire also narrowly edges the Zero in measured roll-on times from 40–60 mph and 60–80 mph, a performance metric in which both bikes easily beat the top-gear acceleration of every gas-powered bike Cycle World has ever tested. To be fair however, it’s an apple-to-oranges comparison; toe a literbike down a couple of gears and see who bears fruit. No petrol cap here. This cover hides the LiveWire’s Type 1 SAE Combo (CCS) DC fast charge inlet. (Jeff Allen /)Seamless, nearly silent acceleration beats a banana in the tailpipe by any measure, but operating range remains the most important EV performance metric. To this end Cycle World Road Test Editor Michael Gilbert methodically tested battery consumption by repeatedly riding a 48-mile loop that includes a blend of 18 freeway miles, stop-and-go city streets, a stretch of the Pacific Coast Highway, and a canyon road. Ridden in similar fashion, each bike completed a lap in Sport, Street, and Eco ride mode settings with the battery fully charged at the start of each lap. The average one-lap consumption for the LiveWire was 48 percent of its battery capacity versus 57 percent aboard the SR/F Premium. Viewed another way, the Harley consumed 7.440 kWh while the Zero used 8.208 kWh per lap. A regimented testing plan meant eliminating battery consumption variables, with both motorcycles ridden on an identical loop, in similar traffic conditions, and comparable weather conditions. (Jeff Allen /)Another consideration is charging options provided by each bike. Both offer Level 1 charging that simply involves plugging the included charge cable into a standard 120-volt household outlet. We found the Zero takes under 9 hours to fully charge from empty on Level 1 while the Harley’s larger RESS requires upward of 12 hours. Things get more complicated when using fast-charge capability. Zero employs Level 2 charging while Harley has opted for faster Level 3 DC Fast Charging technology. Level 2 is currently more widely supported at commercial EV charge stations, and while you can hook the LiveWire up to a Level 2 charger, it will only replenish the battery at the Level 1 rate. With its 6kW integrated charger connected at Level 2, our SR/F Premium required 1.5 hours to achieve a 75-percent charge. Expect upward of an additional hour to reach 100-percent SOC as the Zero’s rate of charge slows when nearing a full charge state to prolong battery service life. While the LiveWire wowed us with a Level 3 recharge from zero to 100 percent in 58 minutes, it comes with a caveat: Harley recommends a 4:1 ratio of four Level 1 charges to every Level 3 fast charge to reduce stress on the RESS. Expending electric energy among oil rigs. (Jeff Allen /)Limiting these electron burners to city life is a disservice to their sporting potential as each comes equipped with fully adjustable Showa suspension, dual four-piston radial-mount calipers up front, and sticky sport radial rubber. A plan was hatched to conduct the final test phase carving some Central California back roads. I met up with Gilbert and our photography/video team in the Central Valley town of Taft for two days of back road bliss. For reasons of practicality the bikes arrived in the Cycle World Nissan van with a full charge. Having ridden the LiveWire at the bike’s Portland, Oregon, international press launch, I was getting my first glimpse of a Zero SR/F in the flesh. The Harley-Davidson’s 4.3-inch TFT dashboard is simple and user-friendly. Additional information is easily accessible and there’s an optional speedometer display with a traditional analog dial gauge. (Jeff Allen /)A brief walk-around of the California-built Zero didn’t provoke love at first sight. The paint finish on our Zero had an uneven overspray texture and unsightly staples visible in an inch gap between the leading edge of the saddle and faux tank give an unfinished appearance. Even the mirrors are flimsy compared to those of the more polished and refined LiveWire. The Zero’s handlebar switch gear appears to be Chinese knockoffs of Aprilia Shiver parts, while the LiveWire makes use of rider-interface components found on premium Harley touring models, utilizing dual thumb-operated joysticks for dash menu selection, phone, and music management, as well as turn-by-turn navigation. The clincher came when I saddled up for my first ride on the Zero and gripped its bars to discover sloppy free play in the left grip, something akin to the slack felt in a throttle twistgrip. Why? The majority of the first of two ride days was spent doing photo passes among an army of grasshopper oil pumps that dominate the Taft landscape. Artistic irony pitting ebikes against a crude backdrop explained veteran staff photographer Jeff Allen. Whatever the case, riding back and forth while trying to remain in focus just doesn’t get any easier than doing so aboard a twist-’n’-go EV with no clutch or gearshift to manage. Burning electrons instead of gasoline has its positives, including ripping without any unnecessary attention. (Jeff Allen /)The best fun came at the end of the day riding a stretch of tight curves in the hills west of McKittrick. Just as Gilbert and I had begun to explore the handling performance and swapped bikes for comparative impressions, the sun set in concert with both bikes’ diminished state of charge as we rode them to empty intentionally. Van loaded, we relocated to an Airbnb in Bakersfield for a night’s rest and recharge. Finding the garage of the residence bursting at the seams with property-owner stuff, we rolled the bikes into the living room for an outlet and awoke 10 hours later to a fully charged Zero and 72-percent state of charge on the Harley. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. Utilizing the ChargePoint app installed on his mobile phone, Gilbert pinpointed the nearest Level 3 charging station. Fortune smiled as the hookup located in a parking stall of Café Rio Mexican Grill was adjacent to Bagels & Blenderz, allowing us to graze during the bike’s 28-minute top-up. Washing down a gourmet breakfast burrito with a high-octane double-shot latte sparked a dim thought in my noggin; for every penny saved at the pump, how much retail expenditure and calories consumed does an EV owner incur? The Zero is the lighter of the two bikes—tipping the CW scales at 502 pounds—and its lighter weight is proven in how it feels during side-to-side transitions, though it lacks a sure-footed feel at full lean. (Jeff Allen /)To preserve our charge for a stint of high-energy depletion in the Sierra foothills, we once again loaded the bikes in the van. Gilbert and I conducted back-to-back runs on each bike through a choice stretch of curves along state Route 155. Here, it became apparent the LiveWire tracks corners with more confidence and precision than the Zero. Tip the Harley in and it holds your chosen cornering line with steadfast conviction while a similar act aboard the Zero results in an uneasy wallow and wiggle when the road surface isn’t billiard-table smooth. Maintaining a relaxed grip on the bars and consciously avoiding leaning upper body weight onto the Zero’s wide one-piece bar helped minimize unwanted steering input. The LiveWire doesn’t require any such kid-glove treatment. Unleash the stopping power. The Zero’s J.Juan four-piston calipers and lighter weight just won out in braking performance, stopping from 60 to 0 in 131.9 feet and 30–0 in 33.6 feet, and with more brake feel at the lever. (Jeff Allen /)Gilbert found the Harley’s Sport mode throttle response most natural and better connected at the right wrist, while also favoring its more pronounced off-throttle regeneration (engine-braking feel) for the lessened reliance on brake pressure to slow to a halt. Important because the LiveWire’s classic wide-blade shaped lever found on its V-twin cruisers feels out of place on this sporty platform, and robs brake feel when you need it most. I preferred the lighter regen of the Zero’s Sport mode, finding it a bit reminiscent of a two-stroke coasting on corner entry. I also found Zero’s two-stage regen interesting in that it increases regen effect when the front brake is applied, delivering a clever form of linked braking. The good news is both bikes offer the ability to adjust certain parameters to your liking and save them to a custom ride mode. The LiveWire customizable settings include power, throttle response, and regen settings from 0 to 100 percent, along with three levels of traction control plus TC off. The Zero’s custom ride modes offer more adjustability—including max speed, power, max torque, closed-throttle regen, and brake regen, as well as three TC settings (Street, Sport, Rain) plus off—but is only accessible through the mobile app, and only allows one custom mode to be loaded at a time. The Harley has three custom presets easily accessible on the dash that can be selected while riding. The end of the road. Draining the battery on either will leave you stranded and searching for an outlet. Thankfully the EV charging network is growing at a rapid pace. ChargePoint—North America’s largest network—is expanding by 2,000 places of charge per month. (Jeff Allen /)I was aboard the Zero late in the day, enjoying the flow with light-handed finesse through the remaining good twisty bits when a sudden loss of power ensued. The Zero goes into limp-home mode for the last 10 percent of charge, with maximum power and peak speed tailing off ever so steadily with each remaining mile. Imagine your liter-class four dropping a cylinder, then another until it’s running on one lung over the final mile before coasting to an anticlimactic halt. The Zero was dead at 67 spirited miles, while the Harley had 12 miles of range remaining and also delivered full performance to the last watt. Again, it was our intent to test comparative range and we intentionally rode them to the end, but if not for the chase van, I can only imagine being stranded roadside with the charge cord in an outstretched hand hoping to flag down a passing motorhome. Owners will certainly learn to plan their rides. Sticker shock aside, these two motorcycles are paving the way for EV motorcycles. (Jeff Allen /)At $21,495 (as tested), reduced sticker shock favors the Zero SR/F Premium. But that isn’t grounds to avoid an honorable discharge and second-in-class ranking. Superior acceleration, sure-footed handling, more range (combined with a quicker charging option), a more complete and intuitive TFT suite with music and navigation all wrapped in an exquisite fit and finish befitting a bike costing $30,149 (as tested) add up to the Harley-Davidson LiveWire being a four-star general of electrics. Dyno numbers on the 2020 Harley-Davidson LiveWire. (Jeff Allen /) Dyno numbers on the 2020 Zero Motorcycles SR/F Premium. (Jeff Allen /)SPECIFICATIONS Harley-Davidson LiveWire Zero Motorcycles SR/F Premium MSRP: $29,799; $30,149 (as tested) $19,495; $21,495 Premium model (as tested) Motor: Revelation internal permanent-magnetic synchronous w/ water-jacket cooling Z-Force 75-10 air-cooled AC motor Battery: 15.5kWh Rechargeable Energy Storage System (RESS) 14.4kWh lithium-ion battery Final Drive: 1-speed/belt 1-speed/belt Cycle World Measured Horsepower: 92.8 hp @ 9,900 rpm 100.2 hp @ 4,480 rpm Cycle World Measure Torque: 74.2 lb.-ft. @ 5,900 rpm 146.5 lb.-ft. @ 1,220 rpm Frame: Cast aluminum Steel trellis Front Suspension: Showa 43mm Separate Function Fork - Big Piston (SFF-BP), fully adjustable; 4.5-in. travel Fully adjustable 43mm Showa SFF-BP; 4.7-in. travel Rear Suspension: Showa Balance Free Rear Cushion-lite (BFRC-lite), fully adjustable; 4.5-in. travel Fully adjustable Showa monoshock; 5.5-in. travel Front Brake: Dual radial-mounted 4-piston Brembo Monoblock calipers, 300mm discs w/ ABS Dual radial-mounted 4-piston J.Juan calipers, 320mm discs w/ Bosch ABS Rear Brake: 2-piston caliper, 260mm disc 1-piston J.Juan caliper, 240mm disc Wheels, Front/Rear: 3.50 x 17 in. / 5.50 x 17 in. 3.50 x 17 in. / 5.50 x 17 in. Tires, Front/Rear: Michelin Scorcher; 120/70-17 / 180/55-17 Pirelli Diablo Rosso III; 120/70-17 /180/55-17 Rake/Trail: 24.5°/4.3 in. 24.5°/3.7 in. Wheelbase: 58.7 in 57.1 in. Ground Clearance: 5.1 in. N/A Seat Height: 31.3 in. 31.3 in. Cycle World Measured Wet Weight: 544 lb. 502 lb. Contact: harley-davidson.com zeromotorcycles.com PERFORMANCE NUMBERS CW Measured Performance Harley-Davidson LiveWire Zero Motorcycles SR/F Premium Quarter-Mile 11.54 sec. @ 110.6 mph 11.83 sec. @ 116.2 mph 0–30 1.47 sec. 1.72 sec. 0–60 3.12 sec. 3.65 sec. 0–100 7.35 sec. 7.70 sec. Top-Gear Roll-On, 40–60 mph 1.17 sec. 1.23 sec. Top-Gear Roll-On, 60–80 mph 1.71 sec. 1.73 sec. Braking, 30–0 33.45 ft. 33.61 ft. Braking, 60–0 133.27 ft. 131.91 ft. Source

2020 Honda CB650R ABS (Honda /)The 2020 Honda CB650R delivers sporty performance in a standard-style package. Its inline-four engine is derived from the popular CBR600RR, but it’s tuned for optimum performance on the street. A notable mid-level machine for riders in the market for a spirited streetfighter. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. 2020 Honda CB650R Reviews, Comparisons, And Competition Honda made the big change to its middleweight standard in 2019, giving it the “R” moniker in place of the “F” and upgrading numerous components throughout. Looks upgrades made it fit nicely among Honda’s “Neo-Sports Café” machines, and improvements to the four-cylinder engine provided a much more enjoyable ride during our first test on the revised machine. That ride also revealed that updates to the CB650R’s suspension resulted in a nicely composed bike through the twisties. It’s a competitive entry against its twin-cylinder rivals in the class from Yamaha (MT-07) and Kawasaki (Z650), though its cost and upgraded components puts it more in league with models like the Ducati Monster 797 and Triumph Street Twin. Honda CB650R Updates For 2020 Honda made no updates to the CB650R in 2020. It’s only available in Chromosphere Red with ABS. 2020 Honda CB650R Claimed Specifications Price: $9,199 Engine: Liquid-cooled, DOHC, four-cylinder Displacement: 649cc Bore x Stroke: 67.0 x 46.0mm Horsepower: N/A Torque: N/A Transmission: 6-speed Final Drive: Chain Seat Height: 31.9 in. Rake: 32.0° Trail: 4.0 in. Front Suspension: 41mm fork; 4.25-in. travel Rear Suspension: Single shock; adjustable preload; 5.0-in. travel Front Tire: 120/70-17 Rear Tire: 180/55-17 Wheelbase: 57.0 in. Fuel Capacity: 4.1 gal. Claimed Wet Weight: 447 lb. Source

2020 KTM 500 EXC-F (KTM/)The 500 EXC-F is KTM’s largest-displacement dual sport model. It’s no secret that we think highly of the 500 EXC-F for its powerful yet controllable engine character, well-rounded WP suspension, nimble handling, light weight, and top-shelf Brembo brakes. In the past 10 years, it has been named Cycle World’s Best Enduro/Dual Sport five times (2012, 2013, 2014, 2017, and 2019). 2020 KTM 500 EXC-F Reviews, Comparisons, And Competition The KTM 500 EXC-F won Cycle World’s 2019 Dual Sport Shootout, which took place in Moab, Utah. While we were riding the red rocks of Moab, we took the time to compare the 500 EXC-F to its smaller-displacement sibling, the 350 EXC-F as well. “The KTM 500 EXC-F is the dual sport to which all others are compared, with the broadest performance envelope,” Cycle World Senior Editor Justin Dawes wrote. “It really is the dual sport for anywhere and everywhere.” Yeah, exactly. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. The 2020 KTM 500 EXC-F retails for $11,399. It costs $100 less than the 2020 Husqvarna FE 501s and $500 more than the 2020 Beta 500 RR-S. KTM 500 EXC-F Updates For 2020 The KTM 500 EXC-F was granted a multitude of changes for 2020. KTM also offers a 500 EXC-F Six Days edition, which is priced at $12,399 and features orange triple clamps, different colored plastics, and special graphics. 2020 KTM 500 EXC-F Claimed Specifications Price $11,399 Engine Liquid-cooled SOHC single-cylinder Displacement 511cc Bore x Stroke 95.0 x 72.0mm Horsepower N/A Torque N/A Transmission 6-speed Final Drive Chain Seat Height 37.8 in. Rake 26.5° Trail N/A Front Suspension 48mm inverted fork, fully adjustable; 11.8-in. travel Rear Suspension Fully adjustable; 12.2-in. travel Front Tire 90/90-21 Rear Tire 120/90-18 Wheelbase 58.3 in. Fuel Capacity 2.25 gal. Claimed Dry Weight 240 lb. Cycle World Tested Specifications Seat Height N/A Wet Weight 255 lb. Rear-Wheel Horsepower 39.4 hp @ 8,100 rpm Rear-Wheel Torque 27.7 lb.-ft. @ 5,200 rpm Source

2020 Harley-Davidson FXDR 114 (Harley-Davidson /)Harley-Davidson went to the dragstrip and fighter jet worlds for inspiration with the FXDR 114, a beefy but sleek Softail with a long, low look, and more cornering clearance than other models in its family. Other elements pushing this cruiser’s performance intent are an aluminum swingarm, a 43mm inverted fork, and a forward-facing air intake, all of which also boost visual appeal too. A chubby 240mm rear tire cements the musclebike vibe, as does Harley’s 114ci Milwaukee-Eight engine—an 1,868cc, four-valve-per-cylinder, 45-degree V-twin that imbues this Softail with performance—78.7 hp and 119 pound-feet of torque on our dyno—while still offering the heavy-flywheel feel. 2020 Harley-Davidson FXDR 114 (Clutch Studios/)2020 Harley-Davidson FXDR 114 Reviews, Comparisons, And Competition When he rode it at the launch, Senior Editor Justin Dawes said, “The FXDR 114 doesn’t look like it should be able to corner well, but it does.” Competition for this bad boy comes from Ducati’s Diavel 1260 S, Yamaha’s venerable VMAX, and possibly Triumph’s new Rocket 3 because of their similar musclebike positioning and focus on power. Harley’s own Fat Bob could be included too. We stacked some of those in a power cruiser comparo. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. 2020 Harley-Davidson FXDR 114 (Harley-Davidson /)Harley-Davidson FXDR 114 Updates For 2020 The only changes to the 2020 FXDR are new color options and a lower base MSRP. 2020 Harley-Davidson FXDR 114 Claimed Specifications Price $18,999–$19,399 Engine Air-/oil-cooled OHV V-twin; 4 valves/cyl. Displacement 1,868cc Bore x Stroke 102.0 x 114.0mm Horsepower N/A Torque 119 lb.-ft. @ 3,500 rpm Transmission 6-speed Final Drive Belt Seat Height 27.7 in. Rake 34.0° Trail 4.7 in. Front Suspension 43mm single cartridge inverted fork; 5.1-in. travel Rear Suspension Preload adjustable; 3.4-in. travel Front Tire 120/70ZR-19 Rear Tire 240/40R-18 Wheelbase 68.4 in. Fuel Capacity 4.4 gal. Claimed Wet Weight 668 lb. Source

From left to right, we have an Amal Concentric, a Keihin PWK flat-slide copy, a Mikuni VM28 from a Yamaha RD350, and a Mikuni TM34 flat-slide. They all share important basic features: 1) a horizontal air passage, flowing from right to left, 2) a vertically movable air slide which throttles the airflow, and 3) so-called center-float design, in which the main jet is central to a fuel bowl with floats that surround or flank the central main fuel jet. (Mark Hoyer/)Carburetion has to be right because only a narrow range of air-fuel mixtures can be ignited in a warmed-up engine, and only a mixture of roughly 12.5-to-1 gives best power. Range Of Ignitable Air-Fuel Mixtures Unless the mixture is leaner than 10 parts air to 1 part fuel, and richer than 18 parts air to 1 of fuel, it can’t even be ignited by a conventional spark ignition system. To give complete combustion of the fuel and best fuel economy, the mixture must be almost 15 to 1, while for best power a mixture of 12.5 to 1 is needed. Because carburetors have a number of overlapping systems, each with its own adjustment range, tuning them to give the desired mixture over the engine’s operating rpm is a step-by-step process. In a cold engine there are no hot surfaces to vaporize the fuel spraying from the carburetors, so the cylinders receive a very lean mixture, plus a combination of wet fuel droplets and a sliding film of fuel wetting the interior walls of the intake duct. Because the ignition spark cannot ignite droplets or wall film, for cold starting the mixture must be radically enriched (or “choked”) so that the small percentage of the fuel that does evaporate forms a mixture rich enough for a spark to ignite. For cold starting the air-fuel mixture may have to be enriched all the way to 1-to-1, and this very rich mixture is provided by using the choke or other carburetor starting system. When the engine fires and runs, its parts warm rapidly from combustion heat, and become more and more able to evaporate the fuel coming from the carburetors, making the mixture grow richer. This is why the engine will emit black smoke and eventually stall if the chokes/starting carb system are left on too long. Carbureted engines of the 1980s and ’90s had to meet exhaust emissions standards so their carburetors are set very lean, leaving almost no safe margin of richness. If the engine is cold and/or the weather cool, this lean mixture can easily be too lean to fire steadily, leading to the familiar “stutter-and-stall” syndrome, and to poor throttle response and surging. These are the usual reasons why people decide to install either high-performance carburetors or jet kits, the latter of which restores smooth operation with the existing carburetors. Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. Before setting up your carburetors, read through this tuning procedure. Then perform the steps carefully, evaluating each aspect of carburetion. It’s tempting to slap on the new carbs and head for the hills, but this can result in a bike that runs far less well than it could if it were systematically tuned. You can avoid such problems, learn a lot about carburetion, and get results that please you. It’s wrong to think that you don’t need smooth carburetion on a high-performance motorcycle. You can’t get off corners quickly or launch strongly from the start line if your machine lacks throttle response or has a lumpy powerband. You can solve many problems by careful carburetion work. There may exist a standard recommended setting for the carburetors you have bought, for the machine you plan to put them on. This can make a good starting point but remember this: Carburetion changes with every alteration in air filters, exhaust system, camshaft, cam timing, and compression ratio. The carburetors don’t magically know what parts you are using on your particular engine, so to get the best results you must fine-tune them to the components you are using. Carburetor Parts Aren’t Cheap In what follows you will see changes of throttle slides, needle jets, and other parts referred to as if they were free. They are not. Having a range of parts suitable to this work will cost some money, and such stopgap measures as trying to “drill out” jets or file throttle slides just create unpleasant surprises for the next user or even for you, the current user. Mikuni VM jets from a pair of carburetors. Small idle jets are on the left. In the center are needle jets. The thick end with the notch is at the bottom of the carb, the thin flanged end accepts the needle and fits neatly into the floor of the main air passage. The main jets (right) thread into the bottom of the needle jets. Jets and needles are numbered for sizing and charts are available to help you tune. (Mark Hoyer/)Definitions So we’ll know what we are talking about, we need definitions of the basic carburetor parts. The round bore of the carburetor, through which air flows to the engine, is called the main air passage, and is located in the main casting. Controlling the airflow through this bore is the throttle slide, a kind of gate sliding in a vertical guideway that is more or less at right angles to the main air passage. In earlier carburetors (Amals, Mikuni VMs, etc.) the throttle slide is cylindrical (commonly referred to as a round-slide carb), but in later designs from the later 1980s and ’90s it may be oval or rectangular in cross-section (known as a flat-slide carb). Airflow through a carburetor is not smooth, but rather a series of sudden gulps, one for each engine intake stroke. In order to cause fuel to flow, such a gulp must first pull the air pressure under the slide down. Because of this, the air volume under the slide affects the speed of the fuel flow response. This flat-slide has a much lower air volume beneath it than do the round slides of earlier carb designs, giving it more immediate response. (Mark Hoyer/)The flaring entry to the main air passage is the carb’s bellmouth (gigantic equivalents are used for ground-testing of jet engines). Attached to the throttle slide to project downward beneath it, and moving up and down with it is a tapered metering rod called the jet needle (abbreviated JN). Its tapered lower part fits into a brass sleeve located below the slide in the bottom of the air passage: This is the needle jet (NJ). Fuel flow from the needle jet is controlled by the tapered needle. Screwed into the bottom of this needle jet is the main jet (MJ). Each of these metering parts—needle, needle jet, and main jet—bears identifying markings. Attached to the bottom of the main casting (or in many pre-1960 carbs, separate from it) is the float bowl. Fuel stands inside this bowl at a level specified in the manufacturer’s instructions. A brass or plastic float, linked to a float needle, serves to maintain a constant fuel level in the bowl. As the bowl fills from the fuel tank, the float rises, pushing its float needle toward its closed position. As the engine takes fuel from the bowl, the float drops, opening the float needle and admitting fuel to restore the correct level. Mikuni VM28 RD350 float bowl and carburetor body. In the bowl (foreground) can be seen the two black plastic floats, each with its projecting pin that lifts the float lever (seen edge-on) as fuel level rises. As engine operation takes fuel from the bowl, fuel level and floats sink, opening the float valve to admit more. Making the float bowl concentric with the main jet (the backlit brass object at 12 o’clock) allows this arrangement to be little affected by acceleration or braking. (Mark Hoyer/)The orifice opened and closed by this float-and-needle action can be quite large in gravity-feed fuel systems, but must be much smaller if a fuel pump is used (for otherwise pump pressure could force the float needle off its seat and overfill the bowl). The desired fuel level is just a few millimeters below the bottom of the main air passage—enough below it so there is no dribble of fuel when the engine is not running, but high enough to respond easily to the partial vacuum generated in the main air passage by engine airflow. Between thumb and forefinger is the float needle, which slides easily in the circular housing seen just below the bright brass main jet. Float needle height is controlled by the floats in the float bowl, lifting the float lever (not seen here) whose tang bears against the float needle. In some carbs the float needle and its orifice are a unit screwed in place, allowing provision of a range of flow rates. Such float valves may be stamped with the orifice diameter in millimeters. (Mark Hoyer/)As air rushes through the main air passage on its way into the engine, it produces a partial vacuum in the carburetor throat, which is the region directly under the throttle slide. The vacuum lifts the fuel that last few millimeters to the top of the needle jet so that it can be stripped off by the fast-moving air and carried into the engine. Carburetor Systems Most carburetors have three fuel-delivery systems. The first is the choke system, which on many Japanese carburetors takes the form of a small and very rich starting carburetor, built into the side of the main casting. When you flip on the choke before cold starting, you are opening the tiny cable-operated throttle of this starting carburetor. The Amal 932 (left) was widely used on British motorcycles in 1960s and ’70s. This Keihin PWK flat-slide copy (center) has been adapted to work as a bolt-on replacement for Amals by JRC Engineering. The Mikuni VM28 (right) round-slide remains a popular replacement carburetor. Small-diameter openings on the edge of the bellmouths? One is for the air jet (bleed air to prevent the main system from enriching with engine rpm). Another supplies air via the mixture needle to the idle circuit. The big ones on the right two carbs about halfway up sends air to the rich starting carburetor ("choke"). (Mark Hoyer/)The second fuel-delivery system is the idle circuit, which controls the mixture at idle and up to approximately 1/8 throttle. Fuel from the float bowl enters the idle tube (projecting downward into the fuel from the main casting), right behind (that is, on the engine side of) the main well in which the needle jet is installed. Engine vacuum lifts the fuel to pass through a small brass idle jet, or pilot jet (PJ), and then mixes with air flowing in from the idle air screw (a threaded brass part with a screwdriver slot at its outer end and a tapered needle at its inner end.) The resulting mixture of idle fuel and air emerges from tiny idle orifices in the floor of the main air passage, immediately downstream of the throttle slide. This idle circuit delivers fuel only at or just above idle, and fades out as the throttle lifts because carb vacuum is no longer strong enough to lift fuel through this circuit. The third fuel-delivery system is the main circuit, which begins to take over mixture control from the idle circuit from about 1/8 throttle upward. It has two main parts. The first is the variable-area jet consisting of the tapered jet needle riding inside the needle jet. The needle is held in the throttle slide by a circlip placed in any one of several (Mikuni VM carb needles have five) tiny grooves in the top of the jet needle. Moving this clip to a lower groove raises the needle, increasing the flow area between it and the ID of the needle jet, allowing slightly more fuel to flow (richer mixture). Conversely, raising the clip lowers the needle and reduces the fuel flow (leaner mixture). The needle jet’s top end is almost flush with the bottom of the main air passage, while its lower end extends down to near the bottom of the fuel bowl where it is held in place by the main jet, which screws into it, plus a retaining washer. The Amal has a choke slide integrated into its main slide, but mixture can also be made richer by pushing down the tickler button (just under the Amal logo). This forces the float down in the bowl and allows fuel to rise high and even to flow out the main jet into the carb throat, which makes the air-fuel mixture richer and can aid cold starting. On the center PWK carburetor, the black knob to the right of the slide adds fuel for cold starting. These chokes are actually a tiny, very rich starting carburetor made in unit with the carb body. (Mark Hoyer/)Fuel enters this main system through the main jet, flows up through the restriction between needle jet and tapered needle, and sprays out into the air stream in the main air passage. As the throttle is opened, admitting more air, the fuel flow path between needle jet and tapered needle also becomes larger until finally, near full throttle, it is bigger than the area of the main jet itself. At this point the main jet becomes the controlling factor in mixture, right on up to full throttle. Keep in mind that all carburetor systems overlap each other. The idle system doesn’t just click off at 1/8 throttle and hand over to the main system, any more than the needle/needle jet combination ceases all influence and hands over to the main jet. The idle system can influence the beginning of the mid-throttle mixture and the needle/needle jet can certainly influence full-throttle operation. In general, however, if we want to tune the mid-throttle region it is the needle height (clip position or needle dimensions) we will alter, while if top-end/full throttle running needs tuning, it is the main jet we will be changing. Other carburetor systems may be present for special applications. When you open the throttle suddenly the mixture leans out because the air rushes into the engine faster than the heavier fuel (650 times heavier). On some emissions-control-era carburetors the settings are so lean that sudden opening of the throttle would lean out the mixture enough to stall the engine. To prevent this, an accelerator pump (usually of the flexible diaphragm type) is operated by throttle movement. As the throttle is opened, this pump delivers an extra squirt of fuel to prevent lean stumble or stalling. With the richer settings commonly used on high-performance and racing carburetor applications, accelerator pumps are usually unnecessary. Certain racing two-stroke applications need a richer top-end mixture than can be supplied by a carburetor with normal systems, so a power-jet circuit is added. This is a secondary main jet, supplied by hose from the fuel bowl, delivering fuel to a tube whose end is just in front of the throttle slide in the upper half of its movement. When the slide nears full-open, high-speed airflow passing over the end of this power-jet delivery tube creates enough vacuum to lift extra fuel that the engine needs through this power-jet system. As a special feature on two-stroke racing engines, there is sometimes a solenoid-operated valve in the power-jet circuit. It is there to give greater control over when the power-jet circuit operates. Engine Condition Before beginning carburetion work you must make sure that your engine is in condition to work with. If you have just completed modifications, be sure that any new parts are correctly installed and timed (cams, ignition). Otherwise you may find yourself blaming your new carburetors for problems which originate elsewhere. Checkout And Installation Inspect your carburetors by removing the float bowls to be sure all main jets, idle jets, needle jets, and float valves are all the same. On new carburetors, I have seen mistakes made in factory assembly—not often, but sometimes. Used carburetors may not have had the best care. Set the idle air screws by first running in each one (clockwise) until it gently bottoms, then backing it out the recommended number of turns. If no starting position is given, set them at one-and-a-half turns open. While the bowls are off you should examine the float levers to be sure that all floats rest at the same height when the carbs are held upside down. The float level will be specified in any instructions. Reinstall all parts and tighten the float bowl screws. With four-stroke carburetors operating off of a single or dual cable rack system, you must now check for synchronization of the throttles. This makes sure that each cylinder receives approximately the same amount of idle air so no one cylinder is trying to run away while others lag behind. Throttle synchronization is a key to good throttle response and overall engine smoothness. A common cause of poor throttle sync on bikes with one cable per carb is synchronizing the throttles with the cables routed one way, then arranging them another way so you can put the fuel tank back in place. The tighter you bend a cable housing, the longer it becomes. On a high-performance carburetor like this, the fuel inlet (double-ribbed brass fitting) is quite large to ensure adequate flow. When diagnosing fuel-flow problems, start with the gas cap, ensuring its vent is not blocked, which creates a vacuum in the tank, starving the carb. Move next to the petcocks. Hold the measuring container below the outlet to measure the flow when you open the valve. Then remove the float bowl’s bottom plug, turn on fuel, and measure the flow again. Run fuel lines without kinks and to avoid rubbing on other components. (Mark Hoyer/)Inspect the rubber coupling or manifolds that hold the carburetors on the engine. It is common for these rubber parts to harden with age, then crack during removal of the original carbs. Examine each one using strong light, both looking and feeling for cracks. Replace as necessary. Nothing is worse for carburetion than an air leak, so take care as you mount and clamp the carbs into place (made easier by a thin wipe of oil from one finger). Tighten the metal carb clamp bands snugly but not so much as to bulge the rubber. The aging of rubber is accelerated by excessive stress—I’ve seen many a carb rubber manifold cut and split by excessive clamp tightening. Once the carbs are in place and throttle cables smoothly routed as before, test to be sure the throttles easily and promptly return to the idle position when you let go of the grip. Some older carburetors mounted by a flange and bolts can be distorted enough by bolt tightening to prevent reliable throttle return. Amal carburetors can have their bodies permanently warped by overtightening. Hook up the fuel lines, making sure they fit closely on the carbs and that there are no splits that could leak—I’ve seen fires from this cause. Put securing clips in place. Make sure that no fuel line is kinked, possibly blocking fuel flow. If the lines are so hardened from age that installation is difficult, now is the time to replace them. Finally, turn on the fuel petcock(s) and wait 30 seconds for the float bowls to fill. If one or more bowls overflow, give a rap with a screwdriver handle to unstick its float valve (this was a regular occurrence with TZ750s). If leakage continues, stop and find the cause, disassembling the carbs if necessary. Fuel on your rear tire is bad and fire is worse. It is best practice to have a capable fire extinguisher near at hand. Start-Up Flip on the chokes/starting carbs and start the engine. Unless the idle jets or idle air screw adjustments are way off, it should start right up, possibly running a little fast or slow because the idle speed adjustment has not yet been done. As soon as the engine runs evenly ease the chokes off and continue the warm-up. Remember—you can’t tell a thing about carburetion until the engine is warm enough to vaporize all of the fuel it is getting. Once the engine is warm you can set the idle speed (unless this is a racebike whose throttle slides close completely when the throttle is dropped). Idle speed is set by screw adjusters which slightly lift the throttles. If the engine doesn’t even fire, you must answer the classic questions: Does it have fuel? Does it have spark? Does it have compression? Before starting your carburetor work, ensure the engine has properly timed spark and good compression. Idle System Tuning As the engine warms up it may begin to show signs of distress if the idle mixture is wrong. If the engine begins to blubber as it warms up, it is probably rich on the idle system because engines run richer as they warm up. In that case, try opening up the idle air screws a quarter turn each using a screwdriver with good fit. If this improves the idle you can try for an even better adjustment, making sure each time to turn each carb’s air screw by the same amount. If you get confused (easy to do with all those screws), stop the engine and start over by running in all the idle screws until they lightly bottom, then back out each one to the desired setting. Take notes if that helps. If all is well, you will find that engine rpm definitely responds to these air screw adjustments. You will find a screw position that gives maximum engine idle speed such that turning the screws either in or out from that position causes engine rpm to decrease. This is the correct position. Think of it this way: The ideal air-fuel mixture makes the most horsepower at a given throttle setting—even at idle. Here is the rule for choosing idle (pilot) jets: If the idle jet inside each carb is correct, this position of highest engine idle speed will be somewhere in the range of one turn open to three turns open. If your engine runs best with the air screws less than one turn open, your idle jets are too small and you should fit one size larger. If your engine idles best with its idle screws more than three turns open, your idle jets are too big and you must fit smaller ones. If you do have to change the idle jets, you must repeat this rpm test to get the new correct air screw setting. Once you have the correct idle jet and air screw setting you can adjust the idle speed with the speed adjuster (if any) that raises and lowers the slide to achieve whatever idle you want. Now you are ready to move on to the next step in carbureting your engine. The Main System And Throttle Slide Now with a warmed-up engine bring the revs up very slowly by just cracking the throttle. This is a test of how well the main system chimes in as the idle system reaches the top of its range, and it is very important to throttle response. Air flowing under the throttle slide creates a partial vacuum above the top of the needle jet, and this lifts fuel up and out of it, to be carried into the engine by the fast-moving air stream. A variety of throttle slides. Each connects to a throttle cable, by which the rider can raise or lower it. From the left, #s 1 and 2 are cylindrical slides, and you can see their cutaway as a smooth arc. A cutaway of 3 measures 3/16 inch higher in the center than at back and sides. On the right are two varieties of flat throttle slides, but both have cutaways. The lower the cutaway, the greater the partial vacuum above the needle jet, and the richer the mixture. (Mark Hoyer/)When the throttle is nearly closed, the strength of this vacuum is determined by what is called the throttle slide cutaway. Cutaway is the measure of how much higher the upstream bottom edge of the throttle slide is than the engine-side edge. If you set a slide on end on a flat surface, you will immediately see the difference. A low cutaway produces more vacuum under the slide to pull more fuel out of the needle jet (richer) while a high cutaway produces less vacuum and so less fuel flow (leaner). The effects of slide cutaway are most important in the range from 1/8 to 1/4 throttle. Slides are stamped with cutaway numbers—small numbers such as 1.5 being rich and large numbers such as 4.5 being leaner. Time was when slide cutaway was measured in sixteenths of an inch, giving a 2.0 slide (think 2/16 of an inch) a cutaway of 1/8 of an inch. Three throttle slides seen from the bottom. The Amal slide on the left has a broached hole through it for a choke slide to enrich mixture for cold starting. The central hole in each slide carries the jet needle. The throttle cable resides in the off-center hole. The angle-milled slots on the left sides of the two round slides engage the idle stop screw; screwing it in raises the slide to admit idle air to set idle speed. Numbers on each indicate cutaway height: Amal is 3, Mikuni round-slide is 2.5 and flat-slide is 4.0. (Mark Hoyer/)If your engine stumbles or seems reluctant to accelerate as you just crack the throttle, the chances are that your slides have a cutaway that is too rich or too lean. How can you tell which it is? There are two methods. The first method makes use of the fact that a richer mixture is needed for acceleration than for steady running. Therefore if the engine stumbles when you open the throttle slowly, but seems a bit better when it is leaned out by being opened that small crack quickly, you can be sure the slides are a bit rich. The second method depends upon leaning out the carburetion by shutting off the petcock. The engine will continue to run on the gas in the float bowls, but it will run leaner and leaner as the fuel level drops. If, when running leaner in this way, the engine responds better to slight opening of the throttle, you know that the slides are too rich. Whichever method you use can give you the right answer about slide cutaway. Remember through this work that this test is concerned with throttle openings from 1/8 to 1/4 throttle. In racing I noticed that while an engine may run best on the track with a slide on the lean side (say, a 4.5) it may not push-start well on that slide, requiring a richer compromise such as a 3.5 slide (push-starts were replaced in GP racing by running-engine standing starts in 1984). Once you have decided which way to go, repeat the test with slides a half-step (for instance, replace a 2.0 with a 2.5 or a 1.5) different from the original. If the response is better but not good enough, change the slides by another half-step and test again. Be sure that you end up with both good running at steady 1/8 throttle and good engine acceleration from idle up to that point. You need both. This is an entering air molecule’s view of a Mikuni VM34 with its slide at about 60 percent throttle. You can see the tapered jet needle hanging from its center. On the right you can see the tip and the slotted head of the idle speed adjuster. At 9 o’clock on the left is the downward-angled idle mixture screw. Just behind it is the vertical ferrule over which the rubber line from the fuel tank petcock slips. (Mark Hoyer/)Checking Mixture On The Needle Next, with the engine fully warmed up, repeat the throttle cracking procedure, but this time continue opening the throttle beyond the 1/8–1/4 throttle range, up toward mid-throttle positions. If the engine happily continues to accelerate smoothly, you are in luck because the needle taper, which is now taking over the control of the mixture from the slide cutaway, is correct or close to correct, and you can move on to actual road testing. You may find it helpful to mark the throttle and housing with throttle positions 1/4, 1/2, and 3/4 to ensure accuracy and repeatability. Use a flexible tape measure and divide the distance from closed throttle to wide open, and divide into quarters. Here are four different jet needles, each with the tiny clip that determines its height in the needle jet. The top groove is position 1, which is the leanest setting because it lowers the needle, making mixture “on the needle” leaner (and vice-versa). In another era, carb needles were brass, sometimes chrome plated for wear resistance. These needles are aluminum that has been eternally surface-hardened by anodizing. Note the obvious differences in taper among the three needles on the right. The greater the taper, the faster the needle enriches the mixture as the throttle is lifted. (Mark Hoyer/)If on the other hand this extra throttle opening makes the engine hesitate or run roughly, you are rich or lean on the needles. To find out which it is, take the tops of the carburetors off, pull the slides, and change the position of the needle retaining clips to raise or lower the needles. Raising the clip lowers the needle, making mid-throttle running leaner. Lowering the clip raises the needle, making mid-throttle running richer. Make changes by one clip position at a time because this is a sensitive adjustment. If the changes you make are correct, you will be able to smoothly accelerate the engine up into the mid-throttle positions, and you will also have good snap throttle response. On the most right-hand of the four slide needles you can see its identifying code. A 6DH4 Mikuni needle begins at a one-degree taper, then steepens to a two-degree taper. These codes can be found in the carburetor manufacturer’s tuning information. Usually that portion of the needle that is in the needle jet during the first 1/3 of slide lift is not tapered, allowing mixture to be controlled by slide cutaway. (Mark Hoyer/)There are those who believe there’s something magical about having the needle clip in the center position (#3 on Mikuni VMs) but there is not. The five clip grooves are there to be used, so don’t be afraid to run with the clip in either the top or bottom groove, if that is where your engine runs best. Looking upstream from the engine side of a Mikuni TM34, you see the jet needle disappearing into the central brass needle jet (this particular needle jet has a semi-circular shroud). On the near side of the carb throat can be seen the tiny idle system orifice, from which at idle issues a mixture of fuel metered by the pilot jet and air controlled by the idle mixture screw (not seen here). (Mark Hoyer/)Needle Jet Tuning Suppose that performance is better with the needle clip at the #2 position than in the middle, and better still at the #1 position. You have run out of clip positions but you wonder if the engine would run better still if there were more clip grooves to try. When this happens, it is time for different needle jets. These come in different sizes and styles, and each one has its numbers stamped on its shank. A typical Mikuni number would be 159 P-2. The first three digits (159) are an arbitrary code that you can look up in their product catalog to find out the style (whether it is for two-stroke or four-stroke, its shroud height, its length). If your machine has 159 style needle jets, stay with 159s unless a good reason to change style is found. This shows the difference in throttle slide cross-section. The Mikuni VM on the left, designed in the 1960s, has a round slide while the flat/oval slide on the right was originally developed to improve throttle response in MX competition. The left-hand carb has a spigot mouth that slips into a matching flexible rubber manifold with a clamp band. The other has a flange mount. Both carbs have centrally located brass needle jets, metered by the tapered jet needle that rises and falls with the throttle slide. (Mark Hoyer/)The second group of symbols indicates the bore size of the jet. A P-4 needle jet is one size larger than a P-2, and the sizing goes P-2, P-4, P-6, P-8, at which point the sizing jumps one letter of the alphabet to Q-0 and the series starts over again. A jump of one needle jet size is a small change, but you shouldn’t jump around in needle jet size by more than a number or two at a time. If your tests do indicate that you must change needle jets, make the change and repeat the throttle roll-on procedure to see if your engine responds better. If it does, try different needle positions to see which is now best. In this way you will find the best needle jet and needle position. Steady Throttle Versus Snap Response Slow roll-on tests give you correct mixture for steady running, but on the road you will also need good snap throttle response for downshifting (throttle blipping) and for quick acceleration. Therefore before beginning road testing you should check the snap response by grabbing a handful to see if the engine accelerates smartly, or if it lags and hesitates. Acceleration requires a richer mixture than steady running, so if there is a problem in snap response, it can be cured by enriching the carburetion in the problem area. Usually a slightly richer slide or richer needle position will cure any acceleration or snap response problem you may run into. Road Testing And The Main Jet Once you have good slow roll-on and snap-throttle response you are ready to begin actual road testing. Ride roads that are familiar to you so you can give some attention to how the engine is running or, for higher speeds, get time on a racetrack. If there are carburetion problems, remember at what throttle position they occur so you can work with the parts that control mixture in that range. This is a Mikuni VM from which the float bowl and floats have been removed. The flat brass object is the float lever, whose two arms are lifted by pins on the black plastic floats (not seen), controlling the fuel-admitting float valve and preventing fuel level from rising higher than desired. At the center is the hex-headed main jet, which screws into and retains the needle jet. Below it, hiding down in its recess, is the pilot or idle jet. All jets are stamped with identifying numbers. (Mark Hoyer/)If everything seems good after your work, you are ready to check mixture at full throttle, where it is controlled by the main jet. The method used for years in racing, before the coming of the laptop and oxygen sensors, is called “making a plug chop.” For this you must run the engine under full load, full throttle, at or near peak rpm for long enough to leave mixture indications on a fresh set of spark plugs. For the sake of public safety and your operator’s license, this cannot take place on public highways! Spark Plug Heat Range Spark plug heat range refers to the operating temperature of the metal plug electrodes. To chug around town, a fairly hot-running plug may be necessary to prevent rapid carbon deposition (occurs below 700 degrees Fahrenheit), but for top-end testing a cooler-running plug is needed to prevent the electrodes from operating hot enough to cause pre-ignition and engine damage (1,750 degrees Fahrenheit). Take care to use plugs of heat range suitable for high-speed operation. At left is a 2011 Harley-Davidson Sportster plug with about 1,000 miles running. Center is a traditional 1974 Norton 850 Commando plug with about 300 miles (note dark shiny surface on plug rim from oil past valve guides). At right is a new plug suitable for 1973 Yamaha RD350 two-stroke. Note shorter reach (length of threaded area). The two plugs on the left are of the projected-tip gap style that places the spark in the path of turbulent fresh mixture in the combustion chamber. (Mark Hoyer/)After a plug chop the indications on the plugs can then be “read” to see if the engine is running rich or lean. Just giving the engine a burst of throttle in lower gears doesn’t expose the plugs to combustion heat long enough to leave readable indications on the plugs, so you will have to find a safe, legal long straightaway where you have room to reach top-end. A racetrack, a disused airport, or a dragstrip are useful for this purpose, if permission can be had. Accelerate to top speed in top gear, then chop the engine dead while pulling the clutch. The engine must not be allowed to idle or it will wipe out the indications on the spark plugs. Coast to a stop, pull the plugs (they are hot so you’ll need the traditional rag to handle them) and compare them with the pictures in any spark plug manufacturer’s color chart. Spark plug reading is a specialized art but in general if the tip of the plug’s ceramic insulator is shiny white and the engine accelerated freely to maximum, the mixture is close to right. Plug reading is seldom practiced in racing today, but peering through an illuminated magnifier to read a plug had a specific goal—to look down the length of the ceramic insulator to see if there is a dark ring around it at some point. Most of the insulator in a well-running engine will operate too hot for carbon to stick, but toward the cooler end (where it seals to the plug body) there should be the dark ring that tells you that some free carbon is being generated by combustion. That can only happen when the mixture is on the safe, rich side. If there is no such ring, you are lean. If the tip of the insulator shows a light brown color mixture in these test conditions is a bit rich and even darker colors indicate more and more richness. If the plugs are a dusty white and the engine misfired or accelerated sluggishly, it is lean. Another main jet tuning method exists—one used by racers for many years. While running at top speed, full throttle, very slightly close the throttle and watch the tach. If the revs pick up slightly, the main jet mixture is rich. Modern plugs use different materials for center electrode—platinum in this case. Years ago the center-wire was made of nickel, and high-current spark discharge rapidly eroded it, causing a recurring need for plug re-gapping. Today’s ignitions with high secondary resistance deliver only the capacitive part of the discharge, greatly reducing gap erosion. Assisting in this is the use of high-melting-point center-wires of platinum or iridium, making possible use of fine wire whose small tip radius reduces the voltage needed to jump the gap. (Mark Hoyer/)For a street machine a slightly rich indication is good, together with steady running on top-end. Leave the bone-white plugs and the last few top-gear rpm to the racers, who are going to change their jets every time the sun goes behind a cloud anyway (modern digital engine management systems do this for you automatically). Make your jet changes and repeat your tests with fresh sets of plugs each time, always using the same heat range. Such work consumes a lot of plugs, so you may want to clean them for reuse as suggested to me years ago by “the Champion man,” Bobby Strahlman: oven cleaner, followed by a water rinse. This is a projected-tip gap style that places the gap in the combustion chamber where it is more certain to encounter ignitable “packets” of swirling air-fuel mixture. This Norton Commando 850 plug has an old-style heavy nickel center-wire. The light color of the ceramic insulator and absence of dark deposit on the center-wire indicate close-to-correct mixture. Oil on the face of the steel shell (which runs comparatively cool) indicates this engine’s oil control is failing. (Mark Hoyer/)Dark plugs will not “clean up” to give a good indication of mixture. Fresh plugs each time. You may find the above confusing because you have always been told that plug insulators in well-carbureted engines should be tan or even chocolate brown. This is true of plugs that have run hundreds or thousands of miles on the street, running some of the time at idle, mostly in the midrange, and only occasionally on top-end. In carburetion testing, however, you are starting with fresh, clean plugs and are running for only a few minutes or laps of a track at most. A plug that shows close to shiny white in these tests will in a hundred miles of street running accumulate a tan deposit using the same main jet. This RD350 plug has never been run, and has the older non-projected gap. To improve exposure of the gap to mixture some tuners used to file away the side electrode to about the midpoint of the center-wire. This plug has shorter “reach” (threaded length) than the Norton 850 plug pictured above, to bring its shell flush with the RD’s combustion chamber. When new, the center-wire has sharp sheared edges. A highly effective ignition will somewhat soften those edges, leaving an eroded area—the spark track. (Mark Hoyer/)If this procedure seems time-consuming and laborious, you should consider that factory carburetion engineers of the past did exactly the same tests on every new design, at some point in its development. When you make changes in your machine, or if you have special carburetion requirements, you can get what you want by using such methods. Source

Dan Riley’s BMW R nineT Pure on side roads outside of Johnson City, Tennessee, for the 2019 Built to Ride Tour. (Monti Smith /)The other builders on the 2019 Built to Ride Tour had plenty of street miles on their bikes. Hugo Eccles built the Hyper Scrambler a few years ago and, being the purpose-built machine that it is, it’s seen some serious road time. Spencer Parr’s DR was his first major build and it, too, has been put through the paces; Tony Prust’s Beemer as well. Dan Riley’s, on the other hand… Well, Dan’s bike was built to race and, up until the tour, that’s all it had really done. Dan Riley wears many hats. His company Gunn Design focuses on photography, graphic design, custom signs, motorcycle builds, and anything in between. Dan’s been riding and competing for years and can ride the wheels off of anything he throws his leg over. His builds always have a classic aesthetic to them, but it’s clear his mind stays on racing. Hookie Co.’s quick-swap gas tank cover with the Gunn Design logo brandished on the side. (Monti Smith /)The build for this bike started about three years ago, converting an R nineT Pure into a machine that could be on display at a show like Handbuilt in Austin, Texas, and then pulled outside to race with the Super Hooligans. It was to be good looking, but also a capable racebike. It has seen a couple of versions before this one, most notably the first, with a 1990 CBR400 gas tank modified to fit. It was close to the look he was after, but it wasn’t perfect. Luckily, there was a company making just what he was after. Dan teamed up with Germany-based Hookie Co., a brand that’s been building custom motorcycles and a kit to transform the BMW R nineT into a custom machine with ease. The kit that was utilized here includes a subframe, a new aluminum fuel tank that works with the stock EFI, a battery tray, air filters, a seat, cargo straps, hardware, and more. But, of course, this isn’t just a bike with a kit, though the kit is quite nice. “The medium is the message” reads across the tires of the BMW. (Monti Smith /)After the kit was installed, the new subframe was modified for use with the dirt-style fender off of a Husqvarna FC 450, and a smaller custom solo seat was made by Saddlemen. The aluminum tank would reduce weight and move the center of gravity more toward the middle of the bike, plus allow Hookie’s trademark quick-swap tank cover to be installed, which Dan reworked with his own graphic. The 19-inch rims were laced to billet hubs from Woody’s Wheel Works, then wrapped in Shinko flat track race rubber. Magura lever and master cylinders were paired with Spiegler brake and clutch lines. A custom exhaust was fabricated, then fit with Rocket Exhaust MX-style mufflers. After all of that, a Rapid Bike tuner was used to make sure the boxer was operating at peak performance. Due to some last-minute personal reasons, Dan wasn’t able to be there in person on the Built to Ride Tour 2019 but, through some help from Tony Prust over at Analog Motorcycles, was still able to get his bike out to Nashville, where we started the tour. But, of course, that meant someone would have to ride it. Having met me only through the internet and phone calls at this point, he trustfully suggested that I pilot his BMW through to Johnson City for him, to which I quickly obliged. Still being a reliable newish BMW, the tool roll on the tank holds the bike’s necessary paperwork. (Monti Smith /)Of course, I hadn’t really thought this through and considered the fact that a racebike might not be the best choice to ride for 200-mile days. Or taken a good look at that Saddlemen seat, for that matter… The bike is an absolute blast to ride, it launches from stops like a scalded dog, but on the highway and longer miles, it’s apparent what it was meant to do. By the third day of the tour, I had borrowed Tony’s bicycle shorts with gel padding on the cheeks, which saved me from further bruising. The Saddlemen seat was great on short rides and would be killer if I were racing, but after a few hours, it became quite punishing. As Dan wasn’t there to campaign for his bike and answer questions like the other builders were, his build didn’t garnish enough votes to take home the win. But as you might expect from a bike that’s been transforming for three years, this one isn’t done yet. With his design history, Dan is great at accentuating the details of his builds, as seen here on his exhaust mounts. (Monti Smith /)Up next on the agenda is getting a set of 17-inch wheels and a café-style full fairing to convert for trackdays. Again, racing is always on Dan’s mind. Magura levers and master cylinders help with both performance and the look of performance. (Monti Smith /) Sign up here to receive our newsletters. Get the latest in motorcycle reviews, tests, and industry news, subscribe here for our YouTube channel. Dan Riley’s BMW R nineT made it through the whole tour with no problems. A very fun ride, even if it was a little punishing at times. (Monti Smith /)For more information on the 2020 Built to Ride Tour, head to builttoridetour.com and be sure to check out invited builders Hugo Eccles’ and Spencer Parr’s builds as well. Source