Clutch is slipping when is hot.

Maybe the hose is disintegrating and plugging up the vent hole, again ??

And , if the master cylinder was all "gunked up" , I bet the slave cylinder is, also.

Jim Van said:

And , if the master cylinder was all "gunked up" , I bet the slave cylinder is, also.

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+1...
Once "some" contamination is found, the whole system needs to be overhauled...

I was out of homw, but I will try to verify the hose and I want to wash the engine to eliminate the residual sintetic oil; but I need to know if there is a product to do it and no damage the engine. If someone knows how wash end the product is welcome; as extra info, in my country we have de Autozone, I will check for their advise.... Thanks for all your recomendation.

if you think that the fluid is not returning to the master. release the pressure at the closest point to the clutch, bleeder or at the line itself. if the pressure is released and the clutch and slave are good, on the center stand in gear(not running) you should not be able to turn the back wheel. using this method you can isolate the restriction by then releasing fluid pressure by cracking a line open at the master. an easy was to eliminate hose or master.

Bad idea, in my opinion, to "wash" the engine. What you are inferring is to completely remove all the oil film from the engine's innards. I don't expect such a product would even exist, as certainly damage would be done with bare metal against metal, with the engine running no less, otherwise how would you circulate the product through the internals?

Just do a couple of oil changes, one now and then again in about 100 miles and see if that helps. If it doesn't, I'd say it isn't an oil issue you have.

Al st1100: I will try to do it this weekend is good, good idea.

Bush: Yes I was thinking about and I agree whit you, bad idea "wash" the engine, I will buy original oil from Honda GN4.... I will made the Al ST100?s proposal if donsn?t work I will change for the original oil and run again. A soon i get the result I will share it (maybe this weekend).... Thanks again.

Any 'dino' oil without the friction modifiers(circle on container is blank in bottom area) will work fine.
Add some MMO(MarvelMysteryOil) to crankcase according to instructions and work the clutch several times while riding LIGHTLY having no real load on motor. Change oil again with oil of your choice(20-50w Vavoline just my choice), should be fine after that.

Hurrraaaa....?????? Finaly...... the bike is working excelent....!!!!!

I will explain the complete story.

Problem:
Whit cool engine bike work perfect 7:00am... but litle by litle when the engine was hot (normal rate) the clutch start slip and the bike loses traction; if you acelerate start a "crank" sound and "jumping", if you stop the bike don?t move; you need to wait 1 or 2 hrs to be cool and the bike run good again What hapend..?
Oil..? syntetic..? fluid ..? slave cilinder..?, master cilinder..? clutch..$$$$ ( no please)....?? Deam...

first I thought that of the synthetic oil from yamaha and additives cause the problem and damage the discs, fortunately this was not the cause

Disassembled the Master Cilinder, slave Cilinder, clean all the parts, change the fluid DOT 4 the fluid was damage and caused oxidized sediment, appearance the part were good... after that....!!!!! Bike had same problem.... Deamm... and now..?

Solution:
Al st1100 (thaks very much..) gave me an idea to develop next procedure.

1) Star the engine, Don?t move the Bike.

2) When engine was hot (needle temperature half or more), I put the first gear I start the problem, the Bike didn?t move... to much revolution but no movment.

3) Turn off the engine

4) Pull the clutch handle bar and keep in this position, in the same time released the pressure using valve bleed on the slave cylinder (1/4 turn), carfull the fluid can splash in the face., close the valve bleed and release the handle bar; tight the Valve bleed and release the handle bar.

5) If the hose is getting presure in this moment you sould have release the extra presure and same time the clutch have bee released.

6) Turn on the engine... put the first gear and surprise.... no more problem... BUT the problem is not over; if you use the next day you will have same issue.
but this helped me to eliminate the idea that problem coming from the clutch, the problemas was on the Master cilinder;
Despite already had cleaned the clutch master cylinder, parts look good, etc for some reason was not working properly.

7) I have a CBR1000F, I change the complete clutch master cilinder, bleed for air on the sistem, pressurizing the sistem... and...no more problem........!!!!!! I have 5 days using in hot condition, trafic, etc... and working perfect. That confirm that the problem was on the clutch master cilinder but this is a minor problem.

8) open a beer....... is time to celebrate.

Thanks aaaallll the guy who spend time giving me ideas..... thanks again.

My mail if you have a doubt: garrido.braulio@gmail.com

Hey everyone, new owner and member here. Sorry to bump such an old thread, but I just picked up a 2002 ST1100 with what I think is the exact same clutch issue described in this thread. After 30 minutes or so the clutch starts slipping, as if not fully disengaged. After letting it cool down for an hour or two, it's back to normal. This is after changing the clutch for a fresh one (or at least that's what the seller told me). The bike sat for a few years so some issues are expected.

I opened up my clutch master and found a lot of sediment and old nasty fluid. I got zero bubbles when pumping the clutch. I took the master apart and was able to clear the relief vent orifice hole (or whatever that is). It was definitely clogged with sediment, but now it is clear. Now it is fully bleed with new fluid. I am still catching up on other maintenance, so I haven't had a chance to confirm if it's fixed, but will let you know. In the mean time I will try to post some pictures to show how I did this.

Here are some pictures of before and after. I used a single strand of wire to dig the sediment out until it poked through to the bore, and cleaned everything really good. Only special tools you need are circlip pliers for taking the piston out of the master cylinder. Again I haven't yet confirmed it is completely fixed, but will report back soon.

maschinenbau said:

Here are some pictures of before and after. I used a single strand of wire to dig the sediment out until it poked through to the bore, and cleaned everything really good. Only special tools you need are circlip pliers for taking the piston out of the master cylinder. Again I haven't yet confirmed it is completely fixed, but will report back soon.

Click to expand...

Hopefully you've sorted it.
It's worth checking the brass bush in the lever that the operating pushrod rests in too. You'll need to remove the clutch lever and the little blighter is in the end. They can and do wear out and they like a bit of grease.
Welcome from Northumberland, England.
Upt'North.

Indeed, I noticed that bushing when I disassembled the master cylinder. Mine was squeaky but not worn, so I added some grease during reassembly. The bike is relatively low mileage at only 24,000 miles, so nothing is very worn yet.

Instead of grease on the bushing, use antiseize metal lubricant, it will last longer and remain in place.
You’ve only addressed one area, you can bet money that your clutch slave cylinder is at least that bad, or worse.
Just something to think about.

When I had my done this spring after using it for four years my clutch and brake fluid needed changing. The mechanic had a "moisture" meter that he dipped the probe in my clutch and brake reservoir's and the thing showed they were contaminated with water. Made a believer out of me as I'm changing the hydraulic fluid every two years like the manual says.

red one said:

When I had my done this spring after using it for four years my clutch and brake fluid needed changing. The mechanic had a "moisture" meter that he dipped the probe in my clutch and brake reservoir's and the thing showed they were contaminated with water. Made a believer out of me as I'm changing the hydraulic fluid every two years like the manual says.

Click to expand...

My clutch I do twice a year.

maschinenbau said:

I am still catching up on other maintenance...

Click to expand...

Glad you have that fixed. As Larry noted, you've cleaned jellied old brake fluid out of half of the system. If you do a search for clutch slave cylinder you will find some pictures he has posted of what happens inside the slave cyl with old fluid.

Here's an article to help you sort out issues w/ your new ride...