| Author | Message | ||
     Portero72 |
08 Uly, 22k miles. CANNOT seem to get a consistent and acceptable feel at the front lever. Pads are new, disc is new, and I have tried bleeding the brakes every way I can imagine. At times, the lever travel is acceptable (but not ideal) and the brakes have a solid feel. Seemingly on the next block, the lever travels halfway back to the handle before any braking occurs, and there is a spongy feel. Pump the lever a few times, and it improves a bit, but it just isn't where I think it should be. Is it time to rebuild or replace the master cylinder? Any ideas? | ||
| Hughlysses |
One thing worth trying I read about many years ago: after you’ve bled the brakes the best you can, try this. Pump up the brakes and hold the lever tightly. Get a bungee cord or something similar and wrap around the lever and handgrip as tightly as possible. Turn the handlebars full left lock (to get the master cylinder as high as possible). Leave the bike overnight like that. The theory is any remaining air bubbles in the system “shrink” under the high pressure in the system and gradually float up the brake line and up to the master cylinder. When you release the lever, the air should be released into the reservoir. | ||
| Mark_weiss |
Air in the system usually produces consistent, undesireable, results. If brake feel is better when things are warm and poor when things are cold, the problem could likely be wear in the master cylinder. When things are warmer, the master cylinder is better able to seal. | ||
| Etennuly |
When you pushed the pistons back to fit the new pads, did you clean the dust and such off from the positions where they retract into the caliper? This can cause binding of the pistons, could possibly trap air. You may need to flush the system with clean new dot4 fluid. May be moisture in fluid. | ||
| Portero72 |
Thanks for the suggestions, guys. Vern- The number of times I have bled that brake pretty much guarantees it is full of new fluid. It was coming out the same color as it was going in when I last did it. Hugh- I tried that overnight trick with a zip tie. The feel improved but is still kinda inconsistent. Roughly every third application of brake produces a spongy feel. What's next? | ||
| Tootal |
I know I've mentioned this on other threads but just in case you haven't seen it, I've found that you can get a bubble in the connection to the master cylinder. The banjo bolt goes through the brake line end housing. This housing can trap a bubble in there causing you fits! Place a rag around the banjo bolt connection and apply the brake lever. Crack the banjo bolt loose enough to see fluid come out. Tighten the bolt and hopefully you got the air out with it. I personally have had this be the problem on a Harley but could be on any bike using this type of connection. | ||
| Portero72 |
Tootal- That may have been the first thing I tried after bleeding the brakes twice. Thanks for the suggestion. | ||
| Portero72 |
Mark- What exactly might be worn in the MC? Never rebuilt one before, but the kit is pretty cheap, so it may be worth a shot. | ||
| Mark_weiss |
The piston can lose its flexibility and fail to seal against the inside of the m/c bore. While unlikely on a motorcycle this new, the master cylinder itself can wear. | ||
| Screamer |
Be certain the disc is not binding after the recent installation ("disc is new"). If the disc is binding and not permitted to run true, it may kick the pistons back slightly. The symptom would be an initial solid lever that loses a half stroke (or some part of a stroke) after a moment or two of riding. This can happen even though there is no indicator of pulsing like might be expected. | ||
| Tootal |
Screamer, good point. As it heats up if it can't expand it will warp pushing the pucks back. That would explain why it's not consistent. | ||
| Portero72 |
Hate it when my disc is bound up. How does one check? Muscle the disc around at the mounting points? | ||
| Etennuly |
Could simply be a worn or damaged o ring in the mastercylinder. Get the kit and try it if you can. | ||
| Hugie03flhr |
I would also look for day light between the pads and rotor. This sounds more like pad knock back rather than air or something wrong with the hydraulic side. Make sure that rotor can wiggle a little on each mount and that it returns to the outer edge with no binding. You have to check it warm and cold. | ||
| Tempest766 |
I too have had a "touchy" front brake that bleeding never seemed to consistently fix. I'm beginning to lean toward piston seat corrosion as a possible problem, so when it's a little bit warmer I intend to completely rebuild the front brake on my 08 uly. I have the feejer to get my two wheel fix while working on the mule. |
