Jump to content
Sign in to follow this  

Brake Bleeding...

Recommended Posts

Okay, so I've read all the posts on here about bleeding the brake but still having some problems.

I've got the caliper hung up higher than the master cylinder, I have a vacuum pump attached to the bleeder, and also squeezing the caliper. It seems as though there is a never ending supply of air and it never seems to stop and the lever never gets stiff, yet it pulls the fluid from the master cylinder and I keep putting more in, of course the vacuum pump is also pulling fluid as well as air... any thoughts? Also, if I don't use the pump, and have no vacuum on the line (clear tubing), I can pump the lever and the fluid moves about 1 to 1.5" in the tube and no bubbles come out so I don't know what gives? I got this master cylinder used from a YZ400 to replace mine, so I'm not totally sure it's good, but it looks fine, and I would think that if it was a bad master cylinder that it wouldn't push the fluid through the tube like it is and also would be leaking the fluid somewhere else... let me know what you guys think.

-Josh

Share this post


Link to post
Share on other sites

Your description sounds like the piston/seals in the master cylinder are worn to beyond specs. It would move the fluid in the lines a little bit until there is some pressure for it to overcome, then it can't push any more because the fluid is leaking around the piston and staying in the resivoir.

Cheers,

Mac

Share this post


Link to post
Share on other sites

Did you grease the threads of the bleeder screw? Otherwise, the vacuum of the Mitivac can pull air around the threads, creating what seems like a never ending supply of air bubbles in the fluid. This happened to me a few times until I either greased the threads or used a bit of teflon.

Share this post


Link to post
Share on other sites
Your description sounds like the piston/seals in the master cylinder are worn to beyond specs. It would move the fluid in the lines a little bit until there is some pressure for it to overcome, then it can't push any more because the fluid is leaking around the piston and staying in the resivoir.

Cheers,

Mac

Well it's moving the fluid a full 1 to 1.5" in the clear tubing, which seems like it equals about what it would be moving in the master cylinder... ???

-J

Share this post


Link to post
Share on other sites
Did you grease the threads of the bleeder screw? Otherwise, the vacuum of the Mitivac can pull air around the threads, creating what seems like a never ending supply of air bubbles in the fluid. This happened to me a few times until I either greased the threads or used a bit of teflon.

I didn't grease them, I had some teflon tape, but heck I removed the screw so many times trying different things that I probably should try the grease method.

-J

Share this post


Link to post
Share on other sites

Okay, for shits and giggles I slapped the old M/C back on, and I had that sucker bled i n 2 minutes with the vacuum pump, so the "100% good condition" used YZ400 M/C I bought from the guy on eBay must need to be rebuilt. This kind of ruins the riding weekend, oh well, live and learn.

Does anyone know where to get M/C rebuild kits besides the Yamaha one that is $25? I paid $25 for the M/C, don't feel like putting $25 into it.

On a side note, I have a HUGE selection of O-ring sizes, do most of them use O-rings? Or is it a special proprietary type seal? (Asking this before I bother taking it apart right now.)

-J

Share this post


Link to post
Share on other sites

Glad you figured it out. I don't know about the Yamaha MC, so can't be of any help there.

Just out of curiosity, if you can bleed old MC and get good pressure, why are you putting the new one on? Can't you ride with the old one?

Cheers,

Mac

Share this post


Link to post
Share on other sites
Glad you figured it out. I don't know about the Yamaha MC, so can't be of any help there.

Just out of curiosity, if you can bleed old MC and get good pressure, why are you putting the new one on? Can't you ride with the old one?

Cheers,

Mac

The master cylinder that is on there, I cannot find a lever to replace my broken lever. I have looked everywhere to no avail. It is a 1993 TT600 Belgarda, and so it was an enduro and the lever has an extra piece for the rear brake light (which I no longer have) but it also acts as the "stop" for the lever. Well all the levers I can find do not have this, so the lever just flops all the way forward once you let go of it if you put a normal lever on. So I opted to switch to a more popular master cylinder where lever selection would be greatly increased.

-Josh

Share this post


Link to post
Share on other sites

Okay....that makes sense. Good luck on getting it up and ready to go!

Cheers,

Mac

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×
×
  • Create New...