I bought a used 09' ZX6r, 11k miles. Brakes seemed to work fine. About a month went by until I got a chance to put new pads on it and flush the lines with new brake fluid. When I went to change the pads and fluid I noticed that the lever was real soft, I could pull it back all the way to the handle. I figured it was just old brakes and it would resolve once I serviced them. I did the pads and fluid myself (first time ever doing that) Afterwards the lever felt great, tight, and I did my first track day on the bike with no issues. The bike sat for a month (I only do track days). When I went to give it a pre track inspection a couple days before the next track day the brake lever was real soft again, just like before I serviced the brakes. I flushed the fluid in the master cylinder only, and the brakes felt great again. A couple days later I did another track day and the brakes felt fine the entire day. About a week after the last track day I tested the lever again and it is soft again just like before! I don't see any leaks and the fluid level is normal. Any ideas about what might be going on?
Gotta properly bleed both master and brakes. Do master first. Once you think you have them correct, put a bungee on the brake and leave it on there for a few days and see what happens. If it loses again, and there's no fluid on the ground/parts, then your bleeding procedure is suspect and you still have air in the system. BTW, leaving pressure on the brake for a day or so will force the remaining air to consolidate, usually at the caliper which makes a final bleed easier...
Bleed from the bottom up.... After both calipers are done refill the system.... Put a ziptie on your lever overnight and then bleed the banjo's under the Master the next AM then the top nipple.... Most Air pockets are between the banjo bolt on the master and the master itself...
So then it's most likely just air in the lines. The first time that I flushed the brake fluid I did the entire system, the master cylinder and both calipers. The second time I did just the master cylinder and it seemed to have fixed the issue until a few days later when the lever was soft again. I used a brake bleeder pump kit. I was careful to try not to get any air in the lines but it could have happened I guess, this being my first attempt at flushing brake lines. I'll try flushing the entire system again. Thanks for the help.
Pump the lever.... Stuff a towel under the banjo up top and crack it open then close real quick.. I bet that's all it is...
Listen to Marc, not me.... I'll have to try the banjo bolt on the master...never tried that before...
Marc, after I pump the lever, do I hold it down while I crack open/close the banjo bolt? Or do I pump the lever, release it, then crack open/close the banjo bolt? Thanks.
Don't "pump" the lever! You pull the lever smoothly while bleeding. If you "pump" the lever you are atomizing the air bubbles. This makes the lever firm up, temporarily, until the atomized bubbles consolidate back it to a big bubble or two. This is a very common mistake made by bike and car mechanics alike.
PUMP it after you take the zip tie off... Hold it in... Crack the banjo and then close it (tighten it) quickly.......
I think we have different definitions. Do not pump (as in squeeze the lever multiple times in quick succession) the lever. Squeeze the lever, then open the bleeder.
may also be time for a master cyl rebuild kit, if you are bleeding correctly, and losing lever over a few days. might be a worn, piston, seal, or the bore on the master itself. if it is the latter, you will need a new master. Ski