Clutch is slipping when is hot.

Hello gentelman... I need you help....!!!

Story:

Last month I buy a ST1100 2002 35,000 miles. When I received the bike I did?t feel any problem on the clutch and run as normal.



For maintenance I changed the engine oil and used Yamaha Synthetic oil, after this maintenance I start to notice a problem?.



When the engine is cold the clutch operate properly; after running or the bike is hot and need turn off the engine (go to bathroom) for some minutes and turn on the bike the clutch start slip and the bike practically no moves; I have to turn off and need to wait (1-2 hrs) until the bike is cold to run again; I read in the hand book that the problem could be the oil additives, I changed it for Motul mineral oil but still de problem?.. in your experience do you have any other recommendation..? A frend in this forum said that he have used syntetic oil whitout problems and change the clutch fluid... but I need more suggetion.



I want to check if is possible to repair in home for basics points before to send to Honda ($$).

Thanks for your support

If the oil has friction modifiers then it will cause the wet clutch of the ST1100 to slip. Change oil and filter to something that does not have friction modifiers and you should be good to go again.

I doubt it is the oil, as the temperature of the oil wouldn't likely make any friction modifiers behave differently. Sounds more like water in the hydraulics (clutch fluid) that needs to be bled out. As the fluid heats up, the water vapourizes and creates air bubbles that reduce the effectiveness of the hydraulics. Does the fluid look honey golden to brownish in colour? That's a sign it needs changing.

I had the same issue with a 97 ST1100 with 40k miles. Worked fine for 15 or 20 miles then no clutch release. Give it all the RPMS you want and go nowhere. Changed clutch fluid, no improvement. What I found was that the system was not able to release hydraulic pressure which increases every time I engaged the clutch. Pull the clutch fluid reservoir cover, slowly depress clutch lever fully and slowly release lever. You should see very small bubbles in the reservoir. No bubbles indicate no hydraulic pressure release is occurring.
I drained the clutch hydraulic fluid, flushed the system, still no joy. Drained the new fluid and pulled both the master and slave cylinders. I removed the internal parts and place both both cylinders in boiling water for about 20 minutes. This softened the years of build up and allowed me to clean out the small return hole in the master cylinder with a very small pointy object. I then carefully ran a fine hone to make sure cylinder seals would function properly. I reassembled using original internal parts, refilled with fresh hydraulic fluid( Dot 4, if memory serves, I'm sure someone correct if I'm wrong). I've put a little over 6k miles and no clutch issues.
Good Luck. Do the bubble test.

Bush said:

I doubt it is the oil, as the temperature of the oil wouldn't likely make any friction modifiers behave differently. Sounds more like water in the hydraulics (clutch fluid) that needs to be bled out. As the fluid heats up, the water vapourizes and creates air bubbles that reduce the effectiveness of the hydraulics. Does the fluid look honey golden to brownish in colour? That's a sign it needs changing.

Click to expand...

If you have air or vapour in the clutch fluid it would prevent you from disengaging the clutch not give less friction I would think.

Gerhard

Thanks Byron; I have the same idea + new ideas.... All clues are welcom. Thanks again.

BUSH : the fluid color is yellow almost honey, as you mentioned is time to change the fluid.
All ideas suggest brake fluid change

NOC : basically you had the same problem in the next few days to change the fluid using your procedure, I'll make your suggestions.


As soon as I get the results I am going to share with the forum .... I really appreciate all your ideas.

GERHARD: Thanks for you idea... I soon is posible I will share the result in the forum.

Well it sounds like you need to perform a complete flush of the hydraulic system and this should take care of the problem.

970mike..... sure all the ideas is around it, next weekend I will aply your ideas. Thanks again.

Keep us posted on your findings and outcome. Best of luck.

Sounds like clutch hose could be the culprit. This happens on vehicles when brake hose becomes week. The hose will become soft/pliable enough after it heats up from normal use, that when pressure is apply the slave cylinder is activated and than the hose gets sucked in/together when the master cylinder is releases. The hose collapsing keeps the pressure applied on the slave.

Just my $,02 and something to think about if the flush/cleaning of the master/slave doesn't resolve the problem.



Sent from my iPhone using Tapatalk

First, thanks Everybody for spend your time and special thanks to NOC.

I finally finished, summary of the story: do the procedure suggested by NOC + brake fluid change suggested by evebody and everything worked perfect.

What I found is that the brake fluid was already badly damaged and this generated a rust colored sediment in the master cylinder which caused the holes and system didn?t work properly...as Noc mentioned.

In my case it was not necessary to change the internal parts only clean perfectly and reassemble; but if you have spare parts on hand is much better, in my case is difficult to get it.

My recommendation would be to start with the master cylinder and if the problem persists continue with the the slave cylinder. I mention it because to desassemble de slave in the 2002 model you need to remove all the covers, loose the muffler just to move it 1cm in order to permit access to third screw... (stupid designers).





Don?t forget.....Review and Change you fluid to avoid a Headache...

Noc said:

I
and allowed me to clean out the small return hole in the master cylinder with a very small pointy object. I reassembled using original internal parts, refilled with fresh hydraulic fluid. I've put a little over 6k miles and no clutch issues.
Good Luck. Do the bubble test.

Click to expand...

+1 on above. A clogged vent hole is I bet the root cause of your problem.
And , it's amazing, but after cleaning everything up and polishing up the bore of the MC, the old seal can usually be used over. I have done this with several of my old bikes, just for the heck of it without a problem, as long as the seal lip looks good and the seal is still pliable. I recently did this on an old GL1100I I purchased recent, and the brake works great now.

I'm happy you got it working. A real lesson in flushing hydraulic fluid every couple of years and often if you live in wet climate. Dot anything collects water like magnets collect iron.

Nice, glad you got it taken care of and the bike is working again.

Deam.... The clutch work perfect only for some days, yestaday I travel almost 100Km... during the morning (7:00am)no problem but when try to retun to my city (14:00) i had the same problem; I need to stop for 1hr to be cool and take the road; fortunately not much use the clutch which allowed me to arrive just in time before the clutch began to slip more.... Master cilinder is ok, slave cilinder ok,... I will to clean de hose buy if somebody have a idea is welcom.... I?m looking de Thread "Clutch butting whe hot" and sound same problem.

Sounds like there is moisture in the fluid and when it gets hot it vaporizes and you begin to feel the clutch slip. A complete fluid change, using a good high heat brake fluid should resolve the issue. I had a similar problem with a car and actually had to go with a synthetic fluid to keep it from boiling.

Is possible, I used DOT 4 that the hand book say, but other option use DOT 5... but my question is why...?

I was thinking that the problem was on the hose; because using the clutch the hose keeps pressure; so I made a test: today I drive to my work only i used the clutch one time and little by little the "clutch" start bitting... really no make me sense.
I read an article that mentioned that the problem could you be when you used synthetic oil... my story: when i buy the bike I didn?t felt any problem; I changed the oil for syntetic and stat the problem... I return for normal oil but maybe the clutch has a film of synt oil.. I don?t know if it is rout cause. What do you think..?

You're right, if you used an oil with a friction modifier then it could take a couple of oil changes before the clutch goes back to acting like it should. The friction modifiers need to be washed out by the new oil and this can take a little time. See how it acts up to the next oil change, it will probably get a little better each time you ride.