Clutch Slipping

Hello Again!

I'm trying to resurerct a new to me 2005. It hadn't been ridden in about three years. I have all the fluids replaced, new clutch and brake lines, all the good stuff.

Well, everything is done, except I'm having this problem where the clutch behaves normally when cold, then when the engine is hot, the clutch starts slipping to the point that the FJR won't go at all. I have bled the clutch, and changed the oil (Good quality motorcycle specific oil).

I'm stumped. :angry:

Clutch engaged = the clutch has locked the transmission to the engine and the motorcycle moves

Clutch disengaged = the clutch unlocks the transmission from the engine and the motorcycle does not move

(Sometimes in the past this was confused when we were talking about clutches so I'm defining the terms at the beginning.)

Air in the clutch hydraulic system will prevent the clutch from fully disengaging. Said another way, the clutch will always be partially to fully engaged and not slipping. Bleeding the clutch master cylinder, slave cylinder and clutch lines will not fix a slipping clutch.

Be absolutely, positively and entirely sure that the oil you used is not an energy conserving oil. This oil would definitely cause your clutch symptoms. Your oil must not have these labels.



If your oil is the correct oil, if nobody has messed with the slave cylinder and push rod then your problem is the clutch assembly. Maybe plates or pressure springs. Hmmm, new clutch and brake lines -- when the engine is hot and the clutch is slipping (carefully) open the clutch bleeder and confirm that it is not pressurized. If it is pressurized when hot the clutch will be disengaged. I can't see a way this could happen but it is worth the check.

One of the symptoms of a bad clutch is when under hard acceleration in higher gears the clutch slips, regardless of hot or cold. The clutch will almost always start failing in this fashion and then gradually get worse, starting to slip in lower gears also. Unless you are Skooter doing slow races all day long with a clutch that has >100k miles on it, it is rare for a clutch to go from good to bad like a light switch.

IMO, you need to go take a long look at the oil bottles that were used for your 'fluids replaced'.

Hey Ion,

Thanks for the tips. I double checked the bottles and I was good to go on those. It was a motorcycle specific oil and the brake fluid was one of those spendy bottles from the motorcycle shop.

I also did what you suggested. I flogged it until it got hot enough and started slipping. I then rode home and cracked the bleed nipple, fluid shot out. I closed it off and went for a ride. The clutch had stopped slipping.

So, I don't know what could cause that. Please check my understanding. That means that the clutch was acting as if the lever was pulled even though it wasn't. Correct? What could cause that? I am at a total loss.

Tim

Did you happen to remove the clutch lever when changing lines or bleeding the clutch? If so, check the push-rod and make sure it's in the brass bushing correctly.

If the lever/push-rod is good, check the master cylinder bleed hole and make sure it's relieving properly and is not plugged...

Good luck!

--G

Freesundae said:

Hey Ion,

Thanks for the tips. I double checked the bottles and I was good to go on those. It was a motorcycle specific oil and the brake fluid was one of those spendy bottles from the motorcycle shop.

I also did what you suggested. I flogged it until it got hot enough and started slipping. I then rode home and cracked the bleed nipple, fluid shot out. I closed it off and went for a ride. The clutch had stopped slipping.

So, I don't know what could cause that. Please check my understanding. That means that the clutch was acting as if the lever was pulled even though it wasn't. Correct? What could cause that? I am at a total loss.

Tim

Click to expand...

Air in the line no doubt.. Just because you didn't "see" it when you cracked the line doesn't mean it wasn't there. I defy anyone to actually see the air escaping prior to fluid flow.

Granted there are on most occasions a burbling or bubbling sound .. once in a while enough of the air can accumulate close enough to the "port" so to speak, you will never notice it's passing. As unlike most of the old fukkers here..it contains no food stuff scented methane..

If the master cull push rod is NOT all the way back when released, it blocks an internal relief port. This allows psi to build when the fluid warms up. If this is happening here, it would disengage the clutch slightly and slip.

This comes from my auto repair experience where an overly tight stop light switch adjustment would cause mild brake application after an extended drive.

YMMV

There is a possibility that you overfilled the clutch hydraulic system when changing the fluid. If the master cylinder is overfilled as the fluid gets hot and expands slightly it has nowhere to go meaning it pressurises the system forcing the slave cylinder to push on the clutch rod this in turn could could release the clutch slightly, causing the clutch to slip. By releasing the bleed nipple after you "flogged it" you have probably let the excess fluid out. I don't think you will have an issue any more. I once came across a GSXR1000 stranded at the side of the road after his front brakes locked on following a fluid change, a small spanner soon got him going again after the hydraulic pressure was released. Hope my explanation make some sense.

Freesundae said:

...I then rode home and cracked the bleed nipple, fluid shot out...

Click to expand...

I did say to (carefully) open the bleeder

Glad you found the issue, hopefully you have also taken care of the root cause. Some things that could have caused your problem are: excessive fill (less likely); internal damage to the clutch hydraulic line causing a flap of damaged rubber to work as a one-way valve (much less likely); trapped air that expands when hot (likely).

The advice about the bronze bushing in the clutch lever pivot is always good even if it isn't related to your slipping clutch. That is one of the much neglected areas that really needs regular service along with the shifter pivot and brake pivot.

Glad to see this is already solved. Overfilling the clutch master cylinder does not leave room for the fluid to expand as it heats. I suspect you should still open the MC cover and make sure the fluid is at the top of the site-glass window, and not above it. A small amount of air under the cover seal keeps the system from pressurizing from heat.