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BMW R100GSPD 1995 , 60000 kms

52204

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Hello, I am the proud owner of a BMW R100 GSPD, 1995. Reliable and agile (60,000km). The problem is that it vibrates around 4000 rpm, and this on virtually all speeds of the transmission. Before 4000 rpm and after 5000 rpm it does not vibrate. The bike is in an A1 state. Would anyone have any idea where these vibrations might come from? Thank you and ride carefully.
 
Vibration is caused by one of two things: mechanical imbalance or combustion imbalance. That bike will likely have a small harmonic mechanical imbalance around 4,200 rpm. Across a broader range of rpm it is almost always caused by a combustion imbalance. So it calls for a fundamental tune up: check/adjust valves, clean carbs, synch carbs, spark plugs, check plug wires etc.
 
Vibration is caused by one of two things: mechanical imbalance or combustion imbalance. That bike will likely have a small harmonic mechanical imbalance around 4,200 rpm. Across a broader range of rpm it is almost always caused by a combustion imbalance. So it calls for a fundamental tune up: check/adjust valves, clean carbs, synch carbs, spark plugs, check plug wires etc.





Thanks for the information it's appreciated. If this is mechanical imbalance what to do? Flyweel swing? Clutch? Thank you Michel
 
Thanks for the information it's appreciated. If this is mechanical imbalance what to do? Flyweel swing? Clutch? Thank you Michel

Mechanical imbalance usually is either there or not, and usually doesn't change much. It is often caused by improper assembly of something. Voni had an R80/7 that had a nasty buzziness when we bought it. Tune up did not change much. After a couple of years of rallies and field events and slow races it needed a new clutch. When I went to install the clutch I found that the three heavy parts, (flywheel, pressure plate, clutch cover) had been improperly assembled so the heavy spots were stacked instead of separated. Upon reassembly that buzz was gone. I have seen some vibration from a build up of carbon on one piston but not on the other. This would be rare.

I really suspect your bike is fine except for a bit of combustion imbalance which can be cured with a thorough, systematic tune up.
 
BMWr100GSPD 1995, 60000 kms

Mechanical imbalance usually is either there or not, and usually doesn't change much. It is often caused by improper assembly of something. Voni had an R80/7 that had a nasty buzziness when we bought it. Tune up did not change much. After a couple of years of rallies and field events and slow races it needed a new clutch. When I went to install the clutch I found that the three heavy parts, (flywheel, pressure plate, clutch cover) had been improperly assembled so the heavy spots were stacked instead of separated. Upon reassembly that buzz was gone. I have seen some vibration from a build up of carbon on one piston but not on the other. This would be rare.

I really suspect your bike is fine except for a bit of combustion imbalance which can be cured with a thorough, systematic tune up.

Hello, I double-checked my timing adjustment, and adjust the carburetors and carburetor timing. I disassembled the carburetors and switch to the ultra-sound. the vibration problem remains. ??
 
Are you certain the vibration is coming from the engine? Could this possibly be a driveline vibration? The u-joints were known to wear out (maybe it was the earlier models?) because of the angle between the gear box and the driveshaft, especially when the bike is ridden solo and unladen. When the bike is loaded up, the rear end squats more and straightens the alignment.
 
If it would be the u-joints in the drive shaft then the vibration are felt the most at the foot pegs at 4th, 5th gear under some load - not at lower gears.

The earliest of my 3 drive shafts replacements was at 90,000km. So I don't think at 60,000km this is the drive shaft.

/Guenther
 
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