The Airheads Beemer Club is a non-profit club reclaiming the 'Legendary Motorcycles of Germany'

Topic-icon ‘83 R100CS weird clunking noise while coasting

  • admiralpepega
  • admiralpepega's Avatar Topic Author
  • Offline
  • R100 Level
  • R100 Level
More
4 weeks 2 days ago #6736 by admiralpepega
I have this strange issue when i am coasting in 1st or 2nd gear, i will feel, NOT HEAR, clunking on my feet. It happens only while coasting. Its hard to explain. So I tried to do some diagnosing. Could it be the transmission? I put the bike on the stand and spinned the rear wheel slowly and could not feel any notchiness. It spinned smoothly. But when i rocked the rear wheel back and forth, there was some clunking/freeplay. Then I realized how I was able the weird clunking noise. If I am on 2nd gear coasting with no throttle and then wack the throttle, I will feel that clunk.

What do you guys think is the problem? I hope its not expensive.

Maybe its loose drive shaft bolts? I checked the bolts by hand and they dont seem loose.

Please Log in to join the conversation.

More
4 weeks 2 days ago #6738 by Wobbly
It could be any part of the drive train, from the gearbox out to the rear wheel bearings. I'd start by peeling the swing arm boot back and then running tests to see if it's forward or to the rear of the U-joint that's under to boot. Or the U-joint itself or loose output flange bolts.

Don't think I'd ride it any further either, until you do that.

Don't hide 'em, Ride 'em !!
#15150

Please Log in to join the conversation.

  • admiralpepega
  • admiralpepega's Avatar Topic Author
  • Offline
  • R100 Level
  • R100 Level
More
4 weeks 2 days ago #6739 by admiralpepega
Replied by admiralpepega on topic ‘83 R100CS weird clunking noise while coasting
Thanks will do. When u get going its perfectly normal. Its really hard to detect but something does not feel right.

Please Log in to join the conversation.

More
4 weeks 2 days ago - 4 weeks 2 days ago #6741 by Wobbly

admiralpepega wrote: Thanks will do. When u get going its perfectly normal. Its really hard to detect but something does not feel right.

There are many issues, that, when you get the RPM up or start rolling fast enough happen so many times per second that they seem to go away. But they have simply smoothed out due to speed. Damage is still being done.

You are saying the noise varies by road speed. That means it's definitely in the wheels or final drive.

How many miles are on the bike ?
How often do you maintenance the drive train ?
Is there any perceptible looseness in the wheel bearings ?
When was the last time the wheel bearings were lubed ?
Are the brake rotors tight and the brakes don't "jump" at low speeds ?
Remember: Do not rule out the front wheel !!

I have every encouragement that the issue will reveal itself to slow, careful, logical, systematic scrutiny. A stethoscope could be an invaluable aid when the bike is on the lift and the wheels are being turned very slowly.

Don't hide 'em, Ride 'em !!
#15150
Last edit: 4 weeks 2 days ago by Wobbly.

Please Log in to join the conversation.

More
4 weeks 2 days ago - 4 weeks 2 days ago #6749 by 8166
When you put the bike on the center stand and moved the back wheel with the transmission in 1st gear, how much free play did you feel? I just did that on my '93 R100GS, and got somewhere between 1/2"-1". When I put it in 2nd gear, the amount increased. I suspect that in higher gears, it would be even more.

What we're feeling, I think, are the gear dogs moving relative to each other, and that movement is perfectly normal. If, as you describe, you're "coasting" in 2nd gear, which I interpret to mean going along under constant throttle opening, then "wack" open the throttle, all you're doing is taking up the free play in a particularly violent manner, one that is not good for your transmission.

However, starting sometime in 1984, BMW started leaving off the output shaft circlip, and the best test for that is to pull the rubber boot off the transmission , push it backward far enough to remove the drive shaft bolts, and separate the drive shaft input flange from the transmission output flange. At that point, with the transmission in neutral, you'll be able to rotate the transmission output flange. If you feel anything but buttery smooth rotation, chances are good that 5th gear has shifted on the output shaft and is busily destroying bearings. You can also drain the transmission gear oil and look for deposits on the magnetic drain plug. There will always be some, but they should have the consistency of flour, and you should not be able to feel any texture when you put some between your fingers and rub.

So do those two tests and let us know what you find. Also tell us how long you've had the bike, and how many miles are on it. And how many miles since the last spline lube. If the answer to that last question is more than 25K, you're due for a spline lube, and the drive shaft has to be disconnected to do it anyway.

8166 Scot Marburger, This email address is being protected from spambots. You need JavaScript enabled to view it.
Last edit: 4 weeks 2 days ago by 8166.

Please Log in to join the conversation.

More
4 weeks 1 day ago #6751 by arni

admiralpepega wrote: I have this strange issue when i am coasting in 1st or 2nd gear, i will feel, NOT HEAR, clunking on my feet. It happens only while coasting. Its hard to explain. So I tried to do some diagnosing. Could it be the transmission? I put the bike on the stand and spinned the rear wheel slowly and could not feel any notchiness. It spinned smoothly. But when i rocked the rear wheel back and forth, there was some clunking/freeplay. Then I realized how I was able the weird clunking noise. If I am on 2nd gear coasting with no throttle and then wack the throttle, I will feel that clunk.

What do you guys think is the problem? I hope its not expensive.

Maybe its loose drive shaft bolts? I checked the bolts by hand and they dont seem loose.


so by "coasting" you mean coasting in gear. throttle closed and clutch engaged?

you posted a sentence that makes no sense. Did you leave out the word "reproduce"?

drive train problems tend to be costly once the damage is done. Catching loose bolt before damage is done, not so much. So hope for a loose bolt.

You do not disconnect the driveshaft from the transmission to lube the transmission input splines unless the plan is to remove the transmission. For a simple clean and lube the transmission, swing arm and possibly subframe are move rearward as a unit about 1 1/2 inches. That is enough clearance for the work.

Please Log in to join the conversation.

Moderators: 8166Wobbly
Time to create page: 1.637 seconds