All:

I have replaced my master cylinder and bled the clutch. Works great for about a day and 1/2 and then the clutch starts slipping. You can tell because the "take" point of the clutch keeps moving out. If you re-bleed you are good for about a day and a half.

Any ideas? Could it be the hose or is there a part on the bike itself that needs to be replaced?

Thanks as always for your help.

Tom

 

Strange, the take point should go inwards with air since air is softer than brake fluid. When the take point goes outwards this is usually a sign that the friction plates becomes thinner and thinner but they shall not reduce as quick as your problem returns.

Did you bleed the pipe connection on the main cylinder as well? This has to be done when the main cylinder is replaced. And the outlet shall point as much upwards as possible during the bleeding.

What were the symptoms before you replaced the main cylinder, was it difficult to put in gears or did it slip as it is doing now?

Perhaps the slave cylinder needs new gaskets as well, it may suck in air.

Giving a second thougt, if the lever is normal after bleeding and air comes on and mix with the fluid, the lever will go out since the volume of fluid and air is larger than fluid only. Does it leak fluid as you can see or is the fluid level constant?

 

If the clutch is slipping, bleeding isn't going to help. If there is air in the lines, it won't conpletely disengage, so you would have full clamping power.

It's next to impossible to get all the air out with the pump the handle method only. Use a Mity Vac and that will pull the air out.. You could do the pump the handle method and then on the last pump hold the handle in overnight with a rubber band or something. Leave the cover off the master cylinder as well. This will allow any trapped air to rise up and out. But the Mity Vac is the way to go.

 

Actually, it would be hard to shift, and hard to get into gear if there was air in the lines. Sounds like the slave cylinder is going bad. Only thing that makes sense, or the new master cylinder you put on isn't allowing fluid back into the reservoir. When you first crack the bleeder, without any pumping of the handle, does fluid squirt out? The slave shouldn't be pushing the clutch on it's own. I have seen some cars do this, and usually it is a bad master cylinder or a sticky slave. Why did you replace the master cylinder anyway?

 

Bike sat for 2 years and the master cylinder was nasty and the fluid was cloudy. I bought the replacement kit for it, and pumped in until the fluid ran clear.

I cannot find a schematic on the slave cylinder, only on the master. (ronayers.com) Are there serviceable parts that I could swap out in there?

It runs like a champ after bleeding so I don't think it is the clutch plates. Ihave been bleeding it like car brakes, pump up, open nipple (fluid shoots out), then shut when the handle touches the grip. Is this right?

Thanks for all the feedback!

Tom

 

Mine sat for two years, and I have no problems with the clutch. I would try putting your old one back on and seeing if there is a difference. Maybe the new one has a seal installed backwards or something. My motto "If it ain't broke..." well, you know. The slave may not be serviceable. But honestly it sounds like a master cylinder problem. I guess you could have a hydraulic line restricting flow when it heats up. I have seen it on cars where the brakes start to seize up while driving because the rubber lines won't allow fluid back to the master cylinder. Anyhow, when it starts to act up try cracking loose the bleeder without touching the lever. If fluid shoots out you have something causing the slave to hold the clutch from releasing. If fluid just trickles out, it may be a slave problem. If it shoots out, get it to act up again, and break the line loose at the master cylinder (CAUTION, BRAKE FLUID EATS PAINT, TAKE EVERY STEP TO KEEP FLUID FROM TOUCHING BODY PANELS) and see if it shoots out there, if not, you may have a bad clutch hose. Otherwise, I would suspect the master cylinder. Does the lever release the same distance when it works good vs. when it does not?

Hopefully this is enough info to troubleshoot your issue. It does not sound like a clutch material problem, but it may end up being one if you try to ride it like this [8D]

 

Dose the clutch lever have free play or is to tight.

 

Clutch is smooth when you pull..does not seem tight. When you first bleed it, it will engage closer to the grip. As time passes it seems to engage farther out from the grip. Then you will get on it, and it will rev up (slip). Once I bleed again, I am good to do. Needless to say I am riding with 10mm wrench![:@]

 

Man, you can't keep riding like that, you are gonna cook your clutch. Try the original master cylinder, flush it real good with new fluid. See if your problem goes away. For some reason your slave cylinder is staying pressurized causing your clutch to stay disengaged.

 

Almost assuredly a lack of free play between the clutch lever and master piston in the extended/applied position. That captures fluid in the system not allowing it to return to the reservoir. It will pull some past the seal cup during bleeding and operation as that seal acts as a one way, pressure assisted seal. When the lever or some other component stops it from returning all of the way, passing the pick-up/return port in the base of the reservoir, it captures fluid in the system and keeps the clutch partially disengaged, getting worse with use and heat. Good luck.