Bleeding issues.

[Saul]

Having trouble bleeding the front brakes on my CBF600.  After I did the calipers it appeared to bleed up fine with no bubbles coming out of the calipers but the lever wasn't that hard, would creep back to the bar.   Brakes do bite but not strong enough for my liking.  I initially thought it must be something I did wrong rebuilding the calipers so I cleaned up the old calipers and put them back on same result.   Still have the lever coming back to the bar.  Have bled and rebled the system but no improvement.    Gave up for today but am going to have one last attempt tomorrow, starting off bleeding the master cylinder then down to the left caliper then right.      I'm a bit stumped really, never really come across this before.  Thinking could be something to do with the ABS pump or perhaps the master cylinder.  Happy enough to rebuild the master cylinder, to be honest I wouldn't mind deleting the ABS system but I want to get to the bottom of what is causing the problem before going to the expense of buying new brake lines although it would be an upgrade.  

[Catteeclan]

Assuming the hoses are still standard, clamp the hose from the master cylinder. If it's still spongy you have air in the cylinder or time for a rebuild.

It can be a bitch getting all the air out. The method I used on the R6 yesterday. Calipers hanging by the pipes. I have a milk bottle with a pipe running into it connected to the open bleed nipple, one side at a time. Topping up the reservoir and allowing the fluid to run through itself. Tapping and moving the calipers around. Once you start to get clear fluid I did up the nipple and operate to level a few time to push some of the pistons out a bit. Clamp the pipe, open the nipple again and push all the pistons home with your hands. Did this a couple of time per side and got a cracking level.

Another is the big syringe connected the open nipple forcing the air and fluid upwards. Cover everything around the res as you will spill some. This way also works well.

 

Have fun.

[Saul]

Cool thanks for that.   Yep the hoses are standard and original so 18 years old now, but are made of unobtainium so if they need to be replaced it will be an ABS delete as I am not that keen on buying used ones.   Given me something to work on now.  I never thought to clamp the line to isolate the Master cylinder.   

[Saul]

48 minutes ago, Catteeclan said:

Assuming the hoses are still standard, clamp the hose from the master cylinder. If it's still spongy you have air in the cylinder or time for a rebuild.

It can be a bitch getting all the air out. The method I used on the R6 yesterday. Calipers hanging by the pipes. I have a milk bottle with a pipe running into it connected to the open bleed nipple, one side at a time. Topping up the reservoir and allowing the fluid to run through itself. Tapping and moving the calipers around. Once you start to get clear fluid I did up the nipple and operate to level a few time to push some of the pistons out a bit. Clamp the pipe, open the nipple again and push all the pistons home with your hands. Did this a couple of time per side and got a cracking level.

Another is the big syringe connected the open nipple forcing the air and fluid upwards. Cover everything around the res as you will spill some. This way also works well.

 

Have fun.

Just been out and clamped the master cylinder line, lever still came back to the bar so that's it, air or rebuild or both.  

[YamaHead]

If it were mine....I'd rebuild the master cylinder & install steel braided lines. Sometimes the original brake lines can develop obstructions internally, trapping air & causing havoc....

[Saul]

25 minutes ago, YamaHead said:

If it were mine....I'd rebuild the master cylinder & install steel braided lines. Sometimes the original brake lines can develop obstructions internally, trapping air & causing havoc....

I am very tempted to do just that to be honest.    I think I will do it in stages though as I will have to bypass the ABS if I go with braided lines as far as I know.    The master cylinder rebuild kit is £30 so will do that first, if that doesn't cure it I will get some braided lines next.    

[Six30]

if it was mine i would take it to a bike shop and let them sort the fucking brakes out

[Six30]

just had a thought @Saul... they recon people talk to plants and they respond...

 

 

why dont you go in your garage and try singing  to the brakes....  video it and post on here.

[Buckster]

You should check online to see how to open the valves on the abs pump for bleeding the system. Also are the front and rear linked at all, you may need to bleed the rear brake as well. Lastly a Mityvac is your friend.

[Saul]

Not linked and bleeding is the same as for a non ABS bike on the CBF600.  I have a speed bleeder as well as a knock off Mitvac type thing, also did it the traditional way, used all three in different attempts.  It's why I think the master cylinder needs to be rebuilt.   

[Renegade]

10 hours ago, Catteeclan said:

Another is the big syringe connected the open nipple forcing the air and fluid upwards. Cover everything around the res as you will spill some. This way also works well.

That's how I always do it.