Odd clutch hydraulic behavior

[AZRickD]

As you may recall, a couple of weeks ago I changed out the clutch pack and bled the system. It went without much difficulty. Last week I had a club ride for the purpose of prepping for our April race. Lots of long rocky, though fairly shallow uphill sections allowed me to test the clutch. All behaved as normal except for some slipping which might have had something to do with using 50/50 dyno/atf. Also, I used DOT3 in the front reservoir before I realized that it wasn't DOT4 (as required) -- but other than some borate esters and a better heat range, there is little difference between them.

I drained the oil and checked the clutch plates. All was fine.

I went to the track today to test everything because we have a desert race next week and didn't want to be caught in the boonies with broken equipment.

I rode for about an hour and noticed that every once in a while I'd work the clutch lever and find it with less resistance. Other times I'd have to pump the lever once to get the pressure up. Uh-oh. If I left the lever fully compressed without pumping, the clutch was lightly engaged.I checked the reservoir and it was full. I did a quick field-expedient bleed (I had my bleed kit handy), and re-filled the reservoir. No improvement.

And then I noticed that the last ten percent of my clutch lever throw was very hard (I'll call it mini-hydrolock).. I opened things up again to see if anything was amiss. I didn't find anything. I rode along and the mini-hydrolock disappeared. I can't recall if I still had to pump during this period. But later, I was pumping again, perhaps every third time I had to use the clutch.

Then I noticed the mini-hyrdolock turn into major hydrolock. I couldn't pull the clutch lever in at all and my clutch wouldn't disengage. I got off the track and headed to the truck. I unbuttoned the master cylinder, gave it a bleed (the clutch lever was free to move if the nipple was unscrewed) all to no effect. I just got done washing the bike and it's still locked up.

I'm going to drain the oil and take the clutch cover off to see what up. Then I'll give it a bleed.

Any timely advise?

 

[PEB]

It's funny some times I can bleed a brake or clutch no problem other times seems like it takes an eternity. Try using a syringe and pushing fluid back up the system, I have better luck getting bubbles to run up than down. I also have had good luck getting little bubbles out the top by violently tapping/flicking the lever back. Good luck!

Paul B

 

[AZRickD]

If it's just a matter of airbubbles getting hot and then locking up, I'm a happy guy. I'm still going to remove the clutch pack just in case (oil is now drained and the bike is on the stand).

If I were to look at the clues of the day, air bubbles might be Suspect Numero One. First we have intermittent mushiness from some stray air bubble that escaped from some nook in the system. Then we have that air bubble getting hot from 12 miles of track work -- thus locking up the system. Maybe. But it's still locked up.

BTW, I did use the syringe routine last time. We'll give it a go.

Any chance that I have some horrific internal slave cylinder or other clutch issues?

Back to the garage.

 

[AZRickD]

I just took off the clutch basket. The basket nut appears to have slipped the retaining washer. It was "hand-tight" when I removed it. Certainly not torqued to spec. That could have added some play into the system.

Now it looks like I need some advice on using that retaining washer. What is the proper technique for getting everything snug and folded over the nut so it won't move?

 

[PEB]

I have never been able to get it bent over nice like the factory does. Perhaps GMP will enlighten us.

 

[AZRickD]

I got mine bent over as far as I could get it but, apparently, it wasn't enough to make it stay put. Imagine if I was on a 50-mile desert ride instead of doing a few laps at the track.

There is very little room to maneuver in there. Once you get the nut tightened, the tab is all but unreachable with enough leverage to get it folded back down. It's a fairly stout piece of stamped steel. I've scored the tab up pretty significantly in my attempts to manipulate it.

 

[gasgasman]

Use a pair of channel lock pliers to bend and seat the tab. The pliers will actually pull up on the tab and bend it over the nut.

Rick.
I would suspect your master cylinder seals are worn out.
When you pull the lever in, the fluid is pushing past the seals and not pushing on the slave cylinder.

If you do bleed from the bottom up, be sure to pull the lever in slightly. There is an "anti-drain back" valve in the master cylinder that remains closed when the lever is released.

I'm Gasgasman and I have approved this message.

 

[AZRickD]

That may be the case, but I'm going to button it all up and re-bleed with DOT3/4.

I have a hunch that my odd clutch hydraulics behavior was caused, in part, by the loose clutch hub.

Failing that, it's off to GoFasters for some rebuild kit(s) - I might as well do the brakes too.

 

[Skidad]

+2 on the channel locks. Works awesome for me on my KTM clutch hub nut.

 

[AZRickD]

+3 on the over-sized Channel Lox. Worked fine. Time to bolt, bleed, re-oil, and test. BTW, the hydro-lok is gone.

 

[AZRickD]

Seems to work. But the clutch is still draggy when I kick it in first gear.

My inch-pound torque wrench isn't top quality. I wonder if my 51 inch-pounds might be a little more. Would over tightening the springs cause the clutch to be a little more grippy than normal?

Other than bleeding (I'm using the syringe method), what can I do to make sure the clutch is making its full movement?

What is the spec on the amount of movement I should expect from the pressure plate?

What adjustments can I make (mechanical or otherwise) to loosen the clutch up a bit?

I have the clutch lever adjusted to have less play than I would like. I don't want to crank it in any more, and will likely back the set screw out a smidge.

 

[gasgasman]

You can't "over tighten" the clutch springs by changing the torque on the spring retainer bolts.
The bolts bottom out on the clutch boss fingers.

It does not take much pressure plate movement to disengage the clutches. When you factor in transmission fluid viscosity, you may run into some dragging concerns.

Some people use 4 stroke valve adjustment shims on the clutch push rod to take up the "slack" and eliminate clutch drag.
In other words, the push rod may be too short.
This could be caused by clutch plate thickness variances or the engine cases being machined differently.

 

[GMP]

Adding a shim to the clutch push rod does nothing but offset the position range that the slave cylinder operates in. The variances in slave position caused by tolerance and plate wear are accounted for by fluid volume, thats the beauty of a hydraulic clutch. The reason you felt the lack of resistance and then the lock is because the slave was moving its operating range outward trying to take up the play from the loose clutch hub (pressure plate is mounted to hub), taking in more fluid, until it finally bottomed out at the end of its travel. When everything is correctly tightened and the travel of the slave is normally in the correct range, short slave travel can be caused by a leak in either the slave or master(usually master), or air in the system that is being compressed. If it is being limited mechanically, by a tolerance problem as Girard describes for example, the lever would become very hard before it hit the bar as you felt.

On some of the '05 TE Husky 4-strokes, the push rod was too short (mfg. flaw) that caused the slave to bottom out at the end of travel just as the clutch was fully disengaged, damaging the slave cylinder. In this case a shim was an easy fix. Never heard of a newer GG to have this problem.

The free play at the lever must be such that the clutch master piston is allowed to fully return. If it is not, the master cannot travel its full range and displace the full fluid volume.

Be carefull torquing the spring bolts, they only need to be just past snug, about 6 Nm. They are just cast posts and I've seen guys snap them off easy. Like Girard said this is not an adjustment, they just bottom out.

As far as the hub nut, bend the washer with channellocks. Bend slightly at first, then move the jaws farther in against the hub for a good bite and square edge bend. To torque the hub nut, lock the countershaft with a section of chain and vise grips, in 6th gear. Be sure your tools are accurate.

Inspect everything including the plates and rebuild the master and slave (slave is just an o-ring). Button it up, bleed, and you should be OK.

Hope this helps.

 

[AZRickD]

Took it all apart, and re-torqued the spring bolts per spec (just beyond snug, it appears).

BTW, the crankcase now has 100% Rotella Synthetic.

I also took the slave cylinder off to see if it was leaking. It was dry. Cleaned off the surfaces to get a snug fit.

A buddy told me that he often has to re-bleed once or twice because that's what it takes to get all of the bubbles out. I poo-pooed him, because I was very through with my by-way syringe method. I did it anyway. Wouldn't you know it? A froth of micro-bubbles appeared in my master reservoir. I gave it a test ride and it behaves better, but there is still some drag. Naturally, it improved as it got warmer.

He's a KTM guy and said he's always had trouble with clutch kits that were other than OEM.

So, here are the symptoms. Let me know if this behavior is in the range for wet clutches.

In gear and clutch in, cold motor, when I roll the bike, the motor rotates.
Kicking in gear there is some resistance.
At idle, when I shift from neutral to 1st, there is a slight RPM drop.

Similar behavior when warm. Just less so.

How much throw should I expect from that rod? What is spec?

This may be moot as I'm considering installing a Rekluse Pro in the next couple of months.

 

[GMP]

I don't know how many bikes you have had but it sounds relatively normal to me. Some drag is expected, its not like a dry clutch. When you lift a cold bike off the stand, put it in gear, and try to push it, it will try to drag the motor over. You will not be able to start it in gear when cold. The plates stick as the bike sits. All that matters is that when its warm it allows you to start it in gear if neccessary, and you can find neutral reasonably easy. I tend to agree in general aftermarket vs OEM plates, OEM always seemed better, but I never had to replace a GG clutch pack. What clutch plates do you have?

When you bleed the system, use a BIG syringe, bigger than the system volume, so you won't have to remove and refill it. Completely fill it and allow all the bubbles to escape. Pull the lever slightly as Girard mentioned and hold it with a loose zip tie on the grip. Remove the slave and compress the piston with a small c-clamp. This gives you less volume to purge. Clean the nipple on the slave and drip some fluid in, what you want to do is not introduce any air that you will have to purge through the system. With the slave off the motor and vertical, purge the system until no more bubbles appear. A second person helps to look and draw fluid out of the master with another syringe.

If this is done correctly, and the master/slave seals are good, nothing can go wrong to limit travel. Travel is a function of master/slave volume ratios, basic hydraulics. If you have an aftermarket clutch pack with thicker/different plates/more overall friction, then this may have affect, but you will not be able increase slave travel by any means other than finding a different (higher volume) master cylinder which is highly unlikely.

Last I checked there was no Rekluse Pro for the GasGas. My friend is a dealer though and I'll check with him.

 

[Loosenut]

I recenty needed to bleed the clutch on my 2000. It would not bleed properly. I ended up removing the circlip holding in the MC plunger and pulling it out of the MC enough to allow hydraulic fluid to flow easily when back bleeding with a syringe. It was a little messy, but I got instant pressure as soon as I reinstalled the plunger and circlip.

 

[AZRickD]

I entered the Kilauea Krusher 3 AMA National Enduro this past weekend.

42 miles of rocks, hills, and clutch feathering.

The Gasser performed flawlessly on more than my fair share of rocky hill climbs.

 

[gasser]

My son replaced all his clutch plates (drive and friction) and springs with new Moose parts and the clutch still slips even with lots of play at the clutch lever. The parts came covered with a sticky oil that was not removed before installing. He uses Shell Rotella syn. oil but I wonder if they've changed the formula since the price just jumped to $22 a gallon at Wally World.

 

[AZRickD]

I'd remove the components and give them a soak and change the oil. See if that help.