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Old 04-16-2012, 05:52 PM   #1
Robbke OP
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R90/6 Gear/Trans whine

Last fall picked up a 76 R90/6 with 34K - no major overhaul done but engine opened up by Max BMW wrench to check for worn parts -

Have been riding this spring and have noticed a gear/transmission whine on cold startup that disappears when clutch lever engaged- all fluids have been replaced within half a dozen rides (this winter) and am concerned that this could foreshadow trouble in the future. As the engine warms up and the bike is rideden, the whine recedes - when the ride is over, barely detectable or nonexistent. Pitch of the whine increases with acceleration.

Has anyone experienced this whine- is it native to this model or R90's? Is it serious or can it possibly be classified as a "personality" trait?

Any/all ideas/theories welcomed.....
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Old 04-16-2012, 07:33 PM   #2
daveoneshot
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My /7 does the same thing, just keep an eye on the drain plug for fuzz and/or flakes of metal. My gearbox got better
with full synthetic BMW gear oil. There are excellent gearbox builders here, I bet a couple will chime in and give more
advice.
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Old 04-18-2012, 09:22 AM   #3
Wirespokes
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Most likely it's bearing noise. As said, pay attention to the drain plug magnet. When you start seeing slivers or chunks on the magnet - time to rebuild it.

Frankly, if it were mine, I'd tear into it now. Bearing whine is the first indication of attention needed. The longer it goes, the more damage to everything else in there. And there's a lot of really expensive parts inside!
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Old 04-18-2012, 01:36 PM   #4
Robbke OP
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Having emailed the former owner, he replied that the whine was present when he owned the bike - he had the transmission rebuilt and re-shimmed. The noise was still present.
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Old 04-18-2012, 02:25 PM   #5
disston
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Whine can be coming from the gears. It can be a sign of problems or not. Because this goes away once trans is warmed I would say it's not a problem.
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Old 04-18-2012, 11:17 PM   #6
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I seem to recall (in the dim recesses of my mind) something about gears whining. Don't remember if that was the newer style or the old originals like yours. I wonder if it has anything to do with the throw-out bearing or the rod? That it fades into nonexistance when warmed up, is the mystery. Straight cut gears do tend to make noise and that's the reason fifth is helical.

It's coming back to me - I think some of the gears tended to be out of round - or wobbled, and that's what caused the whine. The center hole wasn't exactly centered. Is it a cyclical noise or steady?
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Old 04-19-2012, 11:45 AM   #7
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It is not something I really understand. I have been told the hyphoid gears in the rear end of my Ford were what was whining after I ran it for about a mile with no oil. I used that rear for about 30K after this and then replaced the gears and the bearings. It whined, it was pretty loud, it might have been the bearings but I was told it was the gears. It stopped whining when I rebuilt it. So I merely infer that gears can whine. The fact that his whine goes away makes me think there really is not a problem But we haven't been told, or nobody has asked yet, just how long, miles, till the whine goes away? I could ask my machinist housemate some more about this. Sometimes that helps but sometimes I just get his BS. I swear the guy thinks he's God's gift to machines. But sometimes he is pretty good.

How long till whine goes away? And, how about, How loud is this whine?
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Old 04-19-2012, 02:49 PM   #8
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Thanks for all responses so far - the whine is at startup, and varies in volume. Goes away when clutch lever is pulled in. It will sometimes whine as I am riding as I go up through the gears - sometimes louder than other times - I can hear it over the engine noise, but as I usually wear earplugs (and I have not done so recently) maybe I just notice noises a little more.

The volume is not at the shrieking level and I definitely do not grinding- the pitch rises with engine speed. I have brought the bike back home from a ride and the whine was so low in volume as to be virtually non-existent. Two nights ago, I brought it back, let it cool down then started it up three or four times - not a bit of noise.

It does seem rather unpredictable - one thing I have not done yet is check the trans. fluid level but since all fluids have been replaced in January and all my Allen wrenches have gone missing in a recent move, it is a task that I will accomplish quickly.
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Old 04-19-2012, 05:18 PM   #9
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Quote:
Originally Posted by Robbke View Post
Thanks for all responses so far - the whine is at startup, and varies in volume. Goes away when clutch lever is pulled in. It will sometimes whine as I am riding as I go up through the gears - sometimes louder than other times - I can hear it over the engine noise, but as I usually wear earplugs (and I have not done so recently) maybe I just notice noises a little more.

The volume is not at the shrieking level and I definitely do not grinding- the pitch rises with engine speed. I have brought the bike back home from a ride and the whine was so low in volume as to be virtually non-existent. Two nights ago, I brought it back, let it cool down then started it up three or four times - not a bit of noise.

It does seem rather unpredictable - one thing I have not done yet is check the trans. fluid level but since all fluids have been replaced in January and all my Allen wrenches have gone missing in a recent move, it is a task that I will accomplish quickly.
The logical thing to do first would be to check the oil.
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