More clutch problems (no pressure at the lever)

[drca]

Ok, Saturday I had some clutch problems that I attributed to air getting into the system after looping the bike (inconsistent clutch engagement, etc...). So Saturday night I took the master cylinder apart, didn't see anything wrong, but just in case replaced the whole assembly by a spare version I had (altho that spare I was reserving for a project bike and was NOT a NEW unit and had an unknown history).

Put the master cylinder back together, connected to clutch line and pushed some new fluid though the nipple at the engine case level and after a bit of fiddling all seemed good.  (I didn't have any hydraulic fluid handy so I used 5W fork oil with the plan to flush the system with the proper fluid when I get some.)

I went riding the morning, and I dropped the bike (just dropped it on the right side).  And when I picked it up... NO CLUTCH!  Pull at the lever required almost no force and when pulling the lever nothing happened (clutch did not disengage)

There is no apparent fluid leaking around the master or slave cylinder. 

I took the lever off and the cylinder still moves back and forth but it seems that the only force I push against is the one from the return spring inside the cylinder.

When I took the cap of the master cylinder it was full (or close enough considering the space the membrane takes), and when I pump the lever I cannot detect any fluid movement (or bubbles)

My diagnostic is that the conical seal on the cylinder has failed and that I need a NEW rebuilt kit.

Anyone has had similar experience?

DC

[huski]

Do you have free play at the lever before the master cylinder piston moves..If the master cylinder doesn't leak there's nothing wrong with it,sounds like there's not enough fluid in there

[drca]

1 minute ago, huski said:

Do you have free play at the lever before the master cylinder piston moves..If the master cylinder doesn't leak there's nothing wrong with it,sounds like there's not enough fluid in there

When I take the lever off and push the cylinder by hand, I have no pressure buildup (just the push back from the internal spring).  Master cylinder reservoir is full...  I haven't try to push fluid from the slave side yet to see if any bubbles pop up at the master side tho.

Denis

[dan williams]

Basic diagnosing skills. You took the master cylinder apart and it looked OK. Reassemble and look elsewhere. Changing to an unknown master cylinder adds another variable that didn't need to be added. So assuming the master cylinder is OK you are left with the hose and the slave cylinder. If there is a leak further down the system you should lose fluid in the master cylinder every time you pump the lever. You should also see the fluid leaking unless it's the slave cylinder seal in which case it's just going to leak into the transmission. I have no idea of the effect of fork fluid in the hydraulics. It's not anything I'd do. If you don't see leakage along the hose I think your slave cylinder is probably compromised.

Might also explain the variability in operation before.

Edited May 30, 2018 by dan williams
Juxtapositioned master and slave

[drca]

1 hour ago, dan williams said:

Basic diagnosing skills. You took the master cylinder apart and it looked OK. Reassemble and look elsewhere. Changing to an unknown master cylinder adds another variable that didn't need to be added. So assuming the master cylinder is OK you are left with the hose and the slave cylinder. If there is a leak further down the system you should lose fluid in the master cylinder every time you pump the lever. You should also see the fluid leaking unless it's the master cylinder seal in which case it's just going to leak into the transmission. I have no idea of the effect of fork fluid in the hydraulics. It's not anything I'd do. If you don't see leakage along the hose I think your slave cylinder is probably compromised.

Might also explain the variability in operation before.

Yeah, I think it might be time to do a rebuild on both the master and slave cylinders.  Does anybody knows the rebuilt kit part number for the slave? (2013 TXT Pro - Mineral Oil).

Thanks for all the help.

 

[lineaway]

 Buy a used AJP or new. That is probaby you problem. The brand.

[owlit]

I think I would try bleeding the system again. sounds like air or lack of fluid as our friend said earlier. Good luck

[drca]

14 minutes ago, owlit said:

I think I would try bleeding the system again. sounds like air or lack of fluid as our friend said earlier. Good luck

Will do.  How do you insure that there is no air bubbles below the nipple down in the slave cylinder?  Just tap and pray that the bubbles will move up?

 

[d2w]

Create a vacuum (say using a medical-type syringe and some suitably sized tubing) and draw the fluid down. Alternatively use the same syringe to force fluid from the clutch/slave up to the lever/master.

[baldilocks]

Just put the bars to right hand lock so m cylinder is at highest point. Back the adjuster off and keep slowly pumping the lever. If every things correct this has always worked for me

[drca]

Ok... I found what the problem was.

My issue started when I looped the bike a week ago and it fell pretty hard on the right side.  Then it got worse last week when I dropped it again, same side (maybe I should work on not crashing so much). 

Turns out that the clutch line got pinched (and punctured) between the lower triple clamp and the frame when the bike landed on its side.  Air got in the line at the puncture point, causing the loss of pressure at the lever.  With the air in the line, pumping the lever didn't flush any fluid out of the line at the pinched point so there was no apparent fluid leak, making it hard to diagnose the problem.

But it all became apparent once I started pushing new fluid through the bleed nipple and saw the fluid leaking from the line.

Usually the line is routed inside the frame which should prevent this problem, but last time I took the front end apart I just re-routed the line outside the frame for expediency... my mistake.

Good thing is that I had a spare clutch line (too many project bike finally paid off!).  So all is good now.

Thanks again to all for the help.