85 K100RS starter clutch - K-Bikes.com - Excellence in Motion
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post #1 of 14 (permalink) Old Oct 27th, 2013, 2:33 pm Thread Starter
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85 K100RS starter clutch

I suspect my starter clutch on the 85K100RS is broken. The starter is spinning but not engaging the engine. If I put the mc in gear and bump it a few times, the starter engages and the motor turns. I looked at Clymer. It looks rather complicated to fix. I have replaced clutch parts but have not removed the clutch assembly. How much more work is it to remove the clutch assembly and the intermediate housing? How expensive are the parts likely to be?
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post #2 of 14 (permalink) Old Oct 27th, 2013, 2:52 pm Thread Starter
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Anybody know which screen contains the starter clutch parts on the BMW fiche? I did some looking on BikeBandit and had no luck finding it.
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post #3 of 14 (permalink) Old Oct 27th, 2013, 6:31 pm
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Look at the starter clutch post at the bottom of this page. Many have used a detergent in the oil to unstick the starter clutch.

Ron Cooper

91 K75RT
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post #4 of 14 (permalink) Old Oct 28th, 2013, 2:17 pm Thread Starter
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Quote:
Originally Posted by 75RT
Look at the starter clutch post at the bottom of this page. Many have used a detergent in the oil to unstick the starter clutch.
I put 8oz (1/2 can) of Sea Foam in the oil. I keep this around to clean the pilot circuits in the carbs of my 90s Triumphs. Put the mc in 3rd and bump-started it using the hill I live on. Did 20 miles of highway. Immediate improvement. Engine engaged on third hit of starter with a nice clunk. (The sound of death of the sprag clutch on the Triumphs.) Rode a bit more. Sprag clutch seems fine. Now optimistic. Tomorrow will tell if the sprag clutch is cured. Beats tearing the rear end off. Thanks for the tip.
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post #5 of 14 (permalink) Old Oct 28th, 2013, 11:23 pm
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I would drain the Seafoamed oil without too much delay. I think Seafoam is solvent and alcohol. Most people use CD2 detergent and drain quickly.

Ron Cooper

91 K75RT
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post #6 of 14 (permalink) Old Oct 29th, 2013, 3:48 pm Thread Starter
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Quote:
Originally Posted by 75RT
I would drain the Seafoamed oil without too much delay. I think Seafoam is solvent and alcohol. Most people use CD2 detergent and drain quickly.
The sprag is still sticking. Hills are now my friends.


The web site states it is a "petroleum based product" which "will not harm engine components, seals, gaskets, catalytic converters or O2 sensors." And if it is on the web site, it must be true, right?
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post #7 of 14 (permalink) Old Nov 11th, 2013, 3:39 pm Thread Starter
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Update: temperature dependence

I have lived with the sticking sprag clutch for a few weeks. Here is what I have discovered.

If the temp stays at 65 or above, the sprag clutch does not stick.

If the temp drops into the 40s but rises to 55, the sprag clutch sticks but releases after hitting the starter 5 or 6 times. The sprag clutch then works fine.

If the temp drops and stays below 45, the mc must be bumped started. Hitting the starter will not release the clutch. After the motor warms up to operating temps, hitting the starter
will release the clutch and the clutch works fine until the motor cools. The clutch then sticks again.

The Sea Foam has probably had little if any effect. But I have only put on a few hundred miles. Standard wisdom is 500 miles for any effect.
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post #8 of 14 (permalink) Old Nov 24th, 2013, 5:07 am
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An engine oil designed for diesel engines might help, such as Shell Rotella T6. These contain heavier concentration of detergents which will work on the crud on the sprag clutch.

- Robert
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post #9 of 14 (permalink) Old Dec 5th, 2013, 1:57 am
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Starter clutch

Just finished putting my 93 K-100 back together due to the same problem. Mine quit within two days?? The dealer wanted $1500 to fix it so I did it myself. I'm a long time professional mechanic so armed with a Claymer manual, I took it on. It was Quite Involved, But I learned a lot.. My assembly was gummed up with a tan colored foamy mess that looked like oil breather caps when their is moisture in the oil. I was riding about a mile to work and back in 30*-50* temps all winter long. The engine never really warmed up and dissipated the normal moisture present and it mixed with the oil and fowling up the one way bearing in the starter clutch. Two seconds in the parts washer and it was just fine. It was Insane to put back together! I was told the engine and trans had to be removed.. Not So.. The trans and bellhousing can just be removed, BUT as I said It's not for the ill prepared, ill equipped of faint at heart. If I run into this again, I will try to flush the goo out any way I can.
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post #10 of 14 (permalink) Old Dec 5th, 2013, 10:07 am Thread Starter
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Quote:
Originally Posted by Pony
Just finished putting my 93 K-100 back together due to the same problem. Mine quit within two days?? The dealer wanted $1500 to fix it so I did it myself. I'm a long time professional mechanic so armed with a Claymer manual, I took it on. It was Quite Involved, But I learned a lot.. My assembly was gummed up with a tan colored foamy mess that looked like oil breather caps when their is moisture in the oil. I was riding about a mile to work and back in 30*-50* temps all winter long. The engine never really warmed up and dissipated the normal moisture present and it mixed with the oil and fowling up the one way bearing in the starter clutch. Two seconds in the parts washer and it was just fine. It was Insane to put back together! I was told the engine and trans had to be removed.. Not So.. The trans and bellhousing can just be removed, BUT as I said It's not for the ill prepared, ill equipped of faint at heart. If I run into this again, I will try to flush the goo out any way I can.
Thanks for the report.

Symptoms are the same. The starter clutch stuck a few days ago after setting for 4 hours in 32 degree temp. Had to bump start the next day in 50 degree weather. Released after riding 15 miles.

Very frustrating as this was my most reliable cold weather mc. Good down to the mid 20s.

I may try the Rotella next. I am using that in my Triumphs as it is way less expensive.

After that I go with a heavy duty cleaner sprayed thru the starter hole, added to the oil and run a very few miles.
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