Master Cylinder

[mickwinf]

thanks will try these methods, on inspection there seems to be fluid leaking from near the lever so i am suspecting a bad seal, they are all new but pattern items and i was not impressed as a couple of parts didn't fit and i used the old ones. Fluid is being pumped out the nipple so master cyl is working to a certain extent

[hairygit]

If you have fluid leaking out by the lever, the seals ARE NOT doing what they should Mixing old parts and new is a recipe for disaster. From where I see it your options are (1) Dismantle again, get the bore of the cylinder lightly honed, and fit a new genuine seal kit  (2) Buy a new pattern master cylinder from DSS (less than a genuine seal kit) After all, 90% of your braking needs are suppied by the front brake on a dry road, and if something lets go when you really need it You only have one life, don't compromise with brakes, PLEASE

[mickwinf]

Hairygit i agree safety is first priority, the parts i reused was the circlip and washer that hold the piston in, the ones supplied were the wrong size, the bore was honed out and cleaned so at a loss until i dismantle it and check.Thanks for advice everyone, it gets lonely in the shed when things are going wrong!

[mickwinf]

hmmm, tried again tonight, the leak was actually coming from the resovoir top as i had not tightened it properly there seems to be quite a build up of pressure in there when pumping. Tried the syringe method ( sounds like some sort of birth control!) but no better, also tried Bitsa's idea and clamped the hose, this gave a solid lever so it seems to suggest the mastercyl is working. Checked for leaks at all joints, also changed the bleed nipple.Brake does work but lever comes back to the handlebars.Now need more fluid so will leave it for a day or two

[Tomb]

I recently had a problem where I had used pads in my caliper that had worn unevenly, so when pulling the lever the brake worked but only just coz it took up all the lever travel just to straighten the pads up, then when letting go of the lever the pads would push the piston way back in. New pads made a huge difference.

Another bleed method I've used when struggling to bleed coz of air stuck at the bottom yoke mounted ali brake light switch/joining piece, crack the banjo bolts to bleed the air out. Its bloody messy so protect paint and as said, your fingers, but it works

[Johnwebley]

you can always try a reverse fill/prime,


detach caliper,remove piston,fill caliper with fluid,then insert piston,press in,and watch the bubbles appear on the mastercylinder,.

this may be a drastic last resort.

sometimes,if you use just one pad in the caliper,and pump it full,then push the piston all the way in,this also helps to dislodge air .

John