5th-gen clutch won't disengage after fluid replacement

I decided to take the plunge and replace my brake and clutch fluid in my '98 this weekend, and came out with a bit of a problem. The brakes actually went pretty smoothly, with the help of a friend, I was actually able to do both ends without the use of a vacuum bleeder, as mine wasn't holding pressure (Harbor Freight FTL). The clutch, however, didn't go as smoothly. I don't think the fluid had ever been changed in over 20k of riding, and when I opened the reservoir, there was a ton of gunk in the fluid, as well as some crystallized on the rubber diaphraghm. I cleaned off the diaphragm, blotted out as much fluid as I could from the reservoir, and replaced/bled the fluid conventionally until it came through without any bubbles. After closing it up, my clutch lever pulls in with almost no effort, and the clutch won't disengage at all. I left the bike overnight with the lever zip-tied to the bar with no change, so now I'm worried that I might have pulled something through the line and jammed the slave cylinder. Is that even possible, or am I just dealing with a lot of air in the system that needs to be bled out again? Thanks!

(Cross-posted this from the 5th-gen section, sorry for any ruffles feathers)

 

Well, one thing you could try is getting a couple of little syringes, filling one with brake fluid and connecting it to the bleed nipple with the hose from your bleeder. When you crack open the nipple, you compress the syringe and force fluid back up through the M/C. If anything got sucked in, hopefully it gets pushed back out into the M/C. Then use the second syringe to suck all the fluid out of the M/C. Refill the whole system backwards too. Plug in the syringe at the bottom, and push fluid up from the bottom. Since you already refilled the whole system, it shouldn't take much fluid to fill the bottom of the M/C back up. Then top off from the bottle and follow the pump/hold bleeding procedure to get full pressure back in your lever.

Jose

 

Good advice with the back bleeding. I always like doing that to be sure i get all the bubbles out. But i would say if that doesnt work just take your slave and master cylinder off and clean everything up real well with some brakleen in the red can and then bleed it all out. Your clutch will be like new afterwards.

 

I had a similar issue with my vacuum bleeder (Mity-Vac), it basically wasn't sealing all the way at the lid. I put a little more downward pressure on the lid as I twist locked it and it sealed correctly and started working properly, might be the same issue. That being said, I now have speed bleeders on all my clutch slave and calipers on both my bikes and it makes things a lot easier for maintenance. The vacuum bleeder worked great for draining the lines though when I replaced them with SSBLs. Good Luck with your problem.

 

I had the exact same thing happen...exact. I think it has something to do with when you reinstall the slave and the piston gets pushed all the way in by the clutch rod. All I did is pull the slave off again and pump it while holding it in my hand. I used my thumb to put pressure on the piston and I could feel resistance in the lever (careful not to pump the piston all the way out) and reinstalled it making sure the rod went onto the hole in the piston without pushing the piston all the way in. Bleed to get air out. Bingo. Firm clutch.

Note: I did not use a vac bleeder. I did it by hand. Pretty simple job.

 

Kizer, I'll give that a shot when I can get back to my friend's garage. I didn't take the slave cylinder off or anything, but I'm leaning towards a problem with it; I was pushing clean fluid with no bubbles through the line while trying to hand-bleed the clutch. OOTVL, I think the problem I was having was that the bleeder was pulling air in around the bleeder nipple threads, there was air constantly bubbling up through the hose, and I'm sure some of it got into the line. I abandoned the vacuum pump and did the entire brake system by hand for that same reason, it seems to have worked out ok.

 

What you've mentioned is the reason I got the Speedbleeders and don't use the MityVac very much. If you don't seal the bleeder threads it will pull air around them, but I can't imagine how that air would get into the system enough to cause the problem you're having.

 

Sounds like it sucked the piston all the way in. There is a spring behind the piston that keeps this from happening under normal operation, but the vac could have quite easily sucked it all the way back thus preventing fluid from entering the cylinder as you bleed it. Fluid was just flowing right down and out the bleed valve, never building any pressure. Pull the slave off and give the lever a little pump. It will push the piston out a little. Reinstall. Takes about 5min.

Remember not to pump it all the way out or the piston will drop out and fluid will pour out with it.

 

Try using a rubber mallet to slightly tap the area near the slave cylinder, that usually helps free trapped air bubbles that without a little "persuasion" those last air bubbles will never come out. Same thing helps for bleeding the brakes too. Just do not hit to hard.

 

Have you checked if the cluth actually disengages by pulling lever & selecting a gear then turning the rear wheel ? It couldn't be just a simple issue that the fluid was so crap previously that its now so soft you only "think" its not working ! My lever does not feel like there's much effort at all !

Hydraulics are really simple that's why we use them. If the clutch worked before & does not now & assuming that all you did was open & empty the reservoir , then there is not enough fluid in the lines or there is excess air. When the lever is released, the system is open to the reservoir.

Some simple things to do when refilling or replacing fluid, it to get the reservoir top level. So get a small piece of wood 1/2" or more thick & put it under the left main stand foot & put bike on the main stand. Then turn bars full right lock. I use a bungee at this point from the opposite handlebar to the rear footpeg hanger to ensure the the bars can't turn ! Now fill the reservoir & attach a bleed hose/bottle to the bleed nipple & open it. Gravity will take effect & fluid will come out the bleed nipple.
So once clean fluid starts to come out, tighten the bleed nipple & gently just move the lever is very little wiggles, any air will track to the MC feed hole & come out.
If no air then try the lever fully to see what resistance there is. Remember the cluth resistance is provided by the springs in the system, it will NEVER go solid like a brake system !


If you don't think there's enough pressure, then pump the lever multiple times quickly, this will build pressure, even with air in the system.
The tie the lever trick only works in a system where you have pressure, but NOT enough, it compresses the sir bubbles to micro bubbles & they then travel up the hoses to the master cylinder, if you then release the lever the air expands & as it now at the top, little movements of the lever will suck it to the reservoir entry to the MC & you will see the bubbles come out.

Hope that helps.

 

Mohawk, I did what you describe in the first paragraph, no change. From everything I've tried and read, it seems like the slave cylinder piston is stuck, so I'm going to try dislodging that when I go to work on it tomorrow. Thanks for all the help.

 

I found that its better to replace a slave cylinder as the re-build kit almost costs as much as the new part. I love my air-assisted mity-vac, works great for clutches and linked brakes etc...I have tried cleaning old slaves just to have them leak again or never actually pump up...

 

Is the tiny pin hole return orifice in the master reservoir clogged with gunk and spooge? It sounds like you have air in the line, maybe an air bubble in the return chamber of the master that can't get out due to clogged orifice.

 

I haven't actually checked that, as I didn't know there was a return hole. I didn't see any fluid being pushed up when I pulled the lever with the master cylinder cap off, so that could be a factor. Also, bearing in mind that the bike has just over 20,000 miles on it, should I be expecting worn-out slave cylinder seals at this point?

 

My 98 has almost 70.000 miles on it and I never replaced the slave. Just replaced the fluid about every other season.

 

Update: I'VE FIXED SOMETHING! I was able to get back to my friend's garage today, took the slave cylinder off, and the piston had retracted pretty far into the housing. A couple of pumps of the lever had it moving again, and after I re-installed the slave and pumped the lever 10-12 times, it built back up to normal pressure. I think the bigger issue was that there was a TON of air in the line; I bled some air out of the slave cylinder valve, but even with the fluid coming out clearly from there, there were still a lot of air bubbles coming up through the master cylinder. After about 20 minutes of pumping and tapping the lever, plus loosening the banjo bolt and pushing out a bit of fluid, the problem seemed to be gone. Thanks for all the help from everyone who posted!

 

Thats a good thing to have in your bag of tricks, just have a spray bottle of water handy to neutralize the nasty brake fluid. You could also tip-tie the lever to the grip over night sometimes. Glad it worked out, thats why I like to use an air assisted bleeder tool. Once you use one, you won't wana go with-out...

 

Glad to hear you figured it out. I like my mytyvac bleeder too and always use it to flush out the old but i always finish the old fashion way of pump and bleed. I know the air bubbles i see while using the mytyvac have nothing to do with the fluid in the lines but i just like to be sure there is no more air in the line.