Clutch not disengaging?

[Gary C]

Beautiful day for a ride, about 3 hours from home noted that the clutch handle felt "spongy" on the downshift and the gear was either quick to drop in OR damned difficult. Also noted that the clutch engaged from almost immediately to immediately.

Limping home it became increasingly difficult if not impossible to shift down unless I was almost stopped. That is a from any hi to low gear. Towards the end the bike begain to stall as the clutch wasn't disengaging anymore and the brakes were probably working overtime to keep the bike from rolling into traffic.

2001 R1150R, about 38,0000 km on it. The hydraulic reservoir indicates full, no oil was present on the engine or on the ground.

I know that no one has a crystal ball, and tomorrow I call the local shop first before the BMW shop. I've read it can be anything from a warped clutch plate to the system needing to be bleed/changed.

Anybody else have a similar situation/problem/issue in the past and if you did what was your outcome?

Thanks

[keithbw]

Odds are it's the slave cylinder, for confirmation check the fluid in the reservoir. Remove the four screws from the master cylinder cap and if the fluid is very dirty, dark gray, and smells like foul gear oil, it's the slave for sure. Many, many posts on this site regarding the removal and replacement of this part. The age and mileage of your bike also make this the most likely culprit. If the fluid is clean, bleed the circuit until you get good feel at the lever. If the slave is bad you will lose the lever feel again within an hour or so of stop and go riding.

[CycleRob]

Your 2001 vintage bike may have had 9 Canadian winters. Plus, 38,000 km (23,612 Miles) isn't a lot of riding for that time period. Unless the fluid was faithfully and completely changed at least every 2 years, there likely will be serious problems. The very tiny bleedback hole in the master cylinder, because it's a tiny needle sized hole, is the first thing that gets gunked up. Plugged up solid. At this point the clutch begins to not fully release. That continuous load + road speed RPM's stresses the tiny throwout bearing mounted inside the clutch slave piston. After hrs/days/weeks of this sustained stress it eventually overheats the tiny ball bearing and it fails. It is then that the spinning clutch release pushrod begins spinning the clutch slave piston in it's bore. That generates so much heat it boils the moisture normally absorbed by the DOT4 fluid, putting air in the system. Then the clutch lever gets spongy and the clutch doesn't fully release.

That is what happened to my long gone 2002 R1150R, only it was a rotated handguard contacting the clutch lever ball end -not- a clogged bleedback hole that caused the failure. There was silvery, smelly brake fluid in the reservoir at the correct level but the clutch lever had big air. Moving the handguard and bleeding the clutch on the roadside got it back to working normally, but the damage to the slave's tiny throwout bearing and slave housing bore was done. It then began very slowly leaking into the slave cavity. It wasn't until the disassembly to clean and grease the clutch splines at 61,877 miles (99,581 km) that the failure was discovered. Click the Thumbnail pics below to see the old and new/improved slave bearing, it's retainer clip and the mess the slow leak made. Also my creative solution that provides an early warning of any future transmission seal or slave piston failures.



Like keithbw said . . . . get inside that master cylinder reservoir and make it spotlessly clean like THIS. If it looks like rich Columbian coffee, you've been a very bad boy!

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[Gary C]

Gentlemen, thankyou for your replies. Today I call the shop(s) and trailer it there. Once I am told the outcome I'll post on this thread. I only hope it isn't what CycleRob is indicating - egads.

[CycleRob]

I got a PM asking why our bikes need the DOT4 systems serviced so often, every 1 or 2 years, compared to cars . . . that can go 5 years and more without the DOT3 fluid getting dark (contaminated). I wondered about this subtle disparity too, after working on both 2 and 4 wheelers DOT fluid systems for decades. All of my last five 4 wheelers had a hydraulic release clutch and front disk brakes. I remember well removing the slave piston of one vehicle with near frozen fingers in a freezing cold garage cement floor to completely clean the system. It was very easy to remove and disassemble for the carb clean and old toothbrush scrubbing.

The bike/car systems are fairly similar except for the fact M/C master cylinders are exposed to rain and cold weather. The same car parts are protected under the hood where there are often high temperatures around the reservoir cup while the master cylinder pushrod, the piston, high quality, thick rubber dust cover and hidden piston seal are mostly in a year round climate controlled environment. The bike version sees wide temperature swings, mostly in a cold, windy, sometimes wet environment. The rubber dust covers are thin, flimsy and do not seal as tightly as their car counterparts.

Comparing the slave cylinder environments, the car one has a more hostile environment than the OilHead's well protected one on the back of the transmission. The car slave piston is less than half the diameter of the bike slave pistons and it's protected by a very tight fitting, thick rubber, high quality dust cover. The bike versions do not even have that part (!!) relying only on the slave piston's single internal seal to keep the moisture out. The bike dust covers and the lack of one gets my vote as to why the car DOT3 systems can last for over 5 years without the reservoir fluid darkening from water absorption, as is common with M/C DOT4 systems.

On a non ABS bike the DOT4 systems are so easy to purge-n-replace I did them both once a year.

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[georgek]

Gary C, any news, good or bad? A similar thing happened with me and my 2002 R1150R this weekend.
At this point, I'm hoping I did not damage the transmission.

Thanks,
George