RogerRamjet Posted May 27, 2015 Share Posted May 27, 2015 Subject is a 2001 VFR800 w/32k miles. Daily commute of 39 miles. Over the last several months, I've noticed the fluid level in my clutch master cylinder slowly dropping. It's still above minimum, so the "leak" is quite slow. Simultaneously, I've been having to let the lever farther and farther out to engage the clutch, so the friction zone is getting pretty small, resulting in some lurchy starts on hills. It's not slipping, but I thought I'd check it out while I'm doing the 32k maintenance. I pull the clutch basket, and everything looks basically new to me. The friction plates are about .118" (.100" is minimum, standard is .115"-.121"). The disks look practically new. The springs are all within spec as well, so I'm not sure what to replace. The only thing I noticed is that many of the inner plates are almost completely dry, something I wouldn't expect from a "wet" clutch. But I've never done a motorcycle clutch before, so this may be normal. There are no leaks from the master cylinder. I pull the slave cylinder and don't see any drops of brake fluid there, either. Just some oily condensation in the cavity it resides in. I push in the slave cylinder and the master cylinder pops right back up to full. I'm only guessing at this point, but my thought is that the fluid is simply going down to the slave cylinder and the slave cylinder is continually extending because, for some reason, the rod is going farther than normal when the clutch is used, which may or may not be related to the now-small friction zone. Anything else I can check or do while it's all apart? I can't find anything that needs replacing, so I'm not sure what I can do to fix it. Link to comment Share on other sites More sharing options...
The Phantom Posted May 27, 2015 Share Posted May 27, 2015 The slave cylinder piston is sticking in the bore and not returning all the way when you let the clutch out - due to sediment in the clutch fluid forming a binding paste in the slave cylinder bore. Not uncommon. Hold the slave assembly over a bucket, pump the piston out, clean and reassemble with fresh fluid (you could put a seal kit through the slave, they are inexpensive, but a simple clean solved this problem for me). Clutch plates look ok, no obvious glazing. Check the basket tangs for burrs and clean them up if required. Link to comment Share on other sites More sharing options...
Member Contributer swas Posted May 28, 2015 Member Contributer Share Posted May 28, 2015 Roger, Had a similar problem, varnish like coating on the sides of the slave cylinder which didn't fix the leak when polished off with metal polish but a slave cylinder kit fixed it. Clearing the air out of the clutch line was a bigger problem when putting it all back together! A right PITA job compared to brake lines. The leak from the slave cylinder was almost imperceptible but there was no alternative solution. Phantom I think has the solution to the lurchy starts, when the fluid level drops far enough the clutch barely works. I didn't get to the air in the master cylinder valving stage but it was very close! Link to comment Share on other sites More sharing options...
RogerRamjet Posted May 28, 2015 Author Share Posted May 28, 2015 Okay, ordered the slave cylinder rebuild parts, and a new rod just to be safe. We'll see if this fixes the problem... Link to comment Share on other sites More sharing options...
ScottLittle Posted June 1, 2015 Share Posted June 1, 2015 I'm having the same issue on my 97. I was going to order a master cylinder rebuild kit. I guess I should order a slave cylinder kit instead. Link to comment Share on other sites More sharing options...
RedRum Posted June 10, 2015 Share Posted June 10, 2015 Got the exact same symptoms on my 99, pulling the slave when I can find the time. As far as I can tell, there's no need to drain the oil? I'll clean up the slave and flush with fresh fluid, to see if that fixes it without messing around on the RH side of the bike, not having to drain the engine oil would make it a cleaner job. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
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