Front Brakes Building Pressure


08 ZX6R, front brakes building pressure on their own. I just finished this restoration. When I got it, the front brake master cylinder was seized up. (Calipers were not) I cleaned and flushed the whole system. Over a week of sitting on stands, the system would build pressure and Lock the front wheel. I’d bleed it and it would be fine. So I rebuilt the master cylinder with all new internals. It would still build pressure but nowhere near as fast or bad. (Maybe 3 weeks but could still move the front wheel) I bled the system last night. I just took it for its first test ride and after about a mile it completely locked the front brakes. I had to open the bleeder to get it back home. What is causing this?

Nick Tea 6 years 23 Answers 2123 views 0

Answers ( 23 )

  1. Ryan, the rear caliper the piston barely moves correct ? I know it moves but when I was looking over my brakes mine only moved maybe an 1/8″

    • When you press the pedal wheel stops when released should free spin but if there is any bit of air or the fluid seeps by a seal it will lock up

  2. Oem levers? Or aftermarket?

  3. I had the same issue and it was the aftermarket lever, put the oem on and problem was fixed

  4. Have it checked out at a bubbly trapped in the breaks messed my buddy up at 30mph when it lockednup

  5. whoever put china levers on the bike caused the issue.

  6. Swollen cylinder valve seals ?

  7. Bad seal on the master or caliper, its allowing fluid in past the master and down to the caliper without being engaged, the only problem it could be is a bad seal or check valve

    • Same as what I thought, the brake fluid cant flow back to the reservoir thats why it keeps building up pressure, could be a bad seal .. try pressing the lever a hundred times to see if the brake jams or not

  8. Bad lines……rubber inside the lines dry rots and flakes….acts like a check valve or one way valve…..letting fluid go to calipers but not return. Last thing I ever thought it would be on my bike but sure as hell was…..hope this helps bro

  9. bad cheap shitty levers they should be banned !!!

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