Clutch drag when hot---oil fix?

[ediehl]

I've been through some threads on oil preferences here in OC-ville (lots of opinions---what a surprise!), and I've seen some references to my current issue, but I thought perhaps I could start a more focused oil thread.

Background: I just bought an 05.5 950 with 13K+ miles. Clean bike; runs great. When I start the bike up the clutch works perfectly, but after 10 minutes or so it starts dragging just a little. It doesn't shift quite so easily once hot, and at a stop in 1st gear I can feel it wanting to creep forward just a bit. I feel no slippage under power, but the clutch won't disengage 100%.

I dialed the clutch lever further out from the grip, and I cleaned the clutch oil jet. I had high hopes for the latter procedure, but while it may have improved the situation a bit, it still drags a little once up to full operating temp. I'm assuming my 05.5 has the improved clutch shaft, but I only read about that issue after I'd put everything back together. Sadly, I do not know what brand of oil is in the bike now, though the PO told me he'd just changed it, and it looks fresh. I have no problem changing it again, but if there's a brand that has been observed to eliminate the symptoms of hot-950-clutch-drag, I'd sure like to try that brand. I've seen reference to 'Ester' oils, but I don't know what that is, and am not sure if it's good or bad, relating to my clutch-drag symptoms.

I've been using Rotella T synth in my various bikes for a few years now, since it's not so expensive, easily available, and a highly regarded JASO-MA oil built for the tough conditions of diesel engines. As an aside, I was recently surprised with the results when I'd put Rotella T in the primary case of my Buell Ulysses. That should have been an acceptable choice, I'd thought, but I was experiencing grabbiness with clutch engagement, and that issue was rectified when I swapped it out for plain old Harley non-synth primary oil. That was a clutch-grabbiness issue, as opposed to a clutch-drag issue, but it did make me wonder about Rotella T and wet clutches.

I'd love to hear from anyone who has found a resolution for clutch-dragging symptoms such as what I described

[MortimerSickle]

Moisture in the hydraulic system can cause this problem. I had this happen on a Honda. Water droplets in the fluid turn to steam when hot, causing the same condition as when air is in the system. When it cools, the steam condenses back to water, and proper operation returns.

If you have flushed your system with fresh fluid, and still have these symptoms, try taking the slave apart to clean manually. The way this system is set up, the fluid goes from the line right out the bleeder, leaving the fluid in the cylinder largely undisturbed.

Once, just after flushing mine, I took it apart and found water droplets in the cylinder.

[Questor]

I've experienced similar issues with my bike over the past week or so.
It's been over 100 degrees for the past week, and I feel the same "creeping".
Also, it's sometimes hard to get the bike into neutral.

This does not happen when it's cooler.

I'm running Castrol GTX 10-40 non-synthetic that has about 2000 miles on it.
I think I need to switch to a heavier oil...

Let's wait and see what other have experienced.

Q~

[MortimerSickle]

I should also mention that when I bought my KTM, it had 16000 miles on it, and did have some clutch drag. I flushed the system, and reflush a couple of times a year. I have not had any drag since.

Many kinds of mineral oil work just fine, but (groan if you must) I have been using brand X baby oil for 5 years, and the clutch works well.

[v8toilet]

If the clutch jet on your bike has been modified or replaced with one with a larger orifice it will also contribute to more drag.

If you're having trouble hitting neutral when hot or if you have a bit of drag in your clutch you can blip the throttle while attempting neutral from a stand still, or make sure you hit it while you're in motion. These are workarounds and not the solution you are looking for.

[uraberg]

I've had the exact same issue on my triumph sprint. I was using Rotella T6. No amount of clutch adjustments would solve the creep when hot issue. I decided to switch to mobil1, and the problem has not returned for a good 5k miles.

[crofrog]

I switched to Rotella Syn from motorex power synt. I've got this same issue now clutch is dragging neutral is hard to find etc on hot days 90+ F. Never occurred before in all the times of running motorex. Also the gear box feels like crap on clutchless shifts too.

Rotella might be a fine oil but it's to thin when it's hot and doesn't shift very well.

Back to motorex for me.

Chris

[ediehl]

The Rotella T issue was with my Buell, but interesting to hear that a couple others have also experienced clutch issues with Rotella. The suggestion to flush the clutch fluid sounds good to me, but I was surprised to hear 'mineral oil'. Any hydraulic clutch I've ever flushed has required DOT 3/4/5 brake fluid. Guess I better study my shop manual...

[ediehl]

Question for MortimerSickle: You made a comment regarding flushing the clutch cylinder as a separate step. Can I not use a vacuum device at the bleeder valve to suction all the fluid from the entire clutch reservoir, replenishing it up top as I go, just as I normally flush brake or clutch hydraulic fluids on other bikes?

[crofrog]

Originally Posted by ediehl

The Rotella T issue was with my Buell, but interesting to hear that a couple others have also experienced clutch issues with Rotella. The suggestion to flush the clutch fluid sounds good to me, but I was surprised to hear 'mineral oil'. Any hydraulic clutch I've ever flushed has required DOT 3/4/5 brake fluid. Guess I better study my shop manual...

Do _NOT_ use brake fluid in your clutch unless you want to replace it.

[crofrog]

Originally Posted by ediehl

Question for MortimerSickle: You made a comment regarding flushing the clutch cylinder as a separate step. Can I not use a vacuum device at the bleeder valve to suction all the fluid from the entire clutch reservoir, replenishing it up top as I go, just as I normally flush brake or clutch hydraulic fluids on other bikes?

With these clutches you normally will get better results using a large syringe and bleeding from the bottom.

[MortimerSickle]

Originally Posted by ediehl

The Rotella T issue was with my Buell, but interesting to hear that a couple others have also experienced clutch issues with Rotella. The suggestion to flush the clutch fluid sounds good to me, but I was surprised to hear 'mineral oil'. Any hydraulic clutch I've ever flushed has required DOT 3/4/5 brake fluid. Guess I better study my shop manual...

My Honda calls for DOT4 brake fluid, but the KTM specifies mineral oil only.

[MortimerSickle]

Originally Posted by ediehl

Question for MortimerSickle: You made a comment regarding flushing the clutch cylinder as a separate step. Can I not use a vacuum device at the bleeder valve to suction all the fluid from the entire clutch reservoir, replenishing it up top as I go, just as I normally flush brake or clutch hydraulic fluids on other bikes?

Yes, a suction pump works fine, and I have done so myself. But, it will not do any better at refreshing the fluid in the cylinder itself.

If you look at the way the bleeder is positioned, you will see what I mean.

[AdvRonski]

Originally Posted by v8toilet

If the clutch jet on your bike has been modified or replaced with one with a larger orifice it will also contribute to more drag.

If you're having trouble hitting neutral when hot or if you have a bit of drag in your clutch you can blip the throttle while attempting neutral from a stand still, or make sure you hit it while you're in motion. These are workarounds and not the solution you are looking for.

This is EXACTLY what a larger clutch oil jet will do. In my personal experience, the popular .50 size jet causes so much clutch drag when warm that it's ridiculous. The condition of the clutch hydraulic fluid is unlikely to be the culprit in this case.

[MortimerSickle]

From what I have read, an oversized oil jet does seem to be a possible cause of this.

However, moisture in the system is also a well documented cause of this type of problem.