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1969 R69S US Crank Balancer (damper)
Re: 1969 R69S US Crank Balancer (damper)
Firstly BMW have always been very good engineers, but when they get things wrong, they don't like to admit it, and they got it wrong with the R69S.
The device is not a vibration damper, it is a torsion damper, it is there to absorb torsional energy which builds up in the crankshaft at a certain rpm, which if held at a steady speed will literally snap the rear mainshaft like a carrot, in between the rear main bearing and the flywheel, it happened to me with my 1961 R69S outfit holding a steady 55mph/4000 rpm up a long hill in Wales, it went with an extremely loud bang, and definitely could not be fixed at the side of the road.
Mine is an early bike that never had the damper fitted, but I promise you I have one now.
The device was fitted quite early on in the production run so this problem must have shown up quite quickly, neither the R68/69 or the R50/51/60/67 engines ever needed anything like this.
So in my honest opinion, this device is absolutely essential, should be maintained in good condition and definitely not removed.
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Re: 1969 R69S US Crank Balancer (damper)
R69S - R60/2 - R67/2 - R51/3 - R69
Re: 1969 R69S US Crank Balancer (damper)
Thanks for the explanation. I did receive the replacement parts and have re-installed mine. It's definitely a tight fit with the new ring but I doubt the old one was the original as the bike has 40,000 miles on it.niall4473 wrote: ↑Sun Dec 19, 2021 7:07 am...
The device is not a vibration damper, it is a torsion damper, it is there to absorb torsional energy which builds up in the crankshaft at a certain rpm, which if held at a steady speed will literally snap the rear mainshaft like a carrot, in between the rear main bearing and the flywheel, it happened to me with my 1961 R69S outfit holding a steady 55mph/4000 rpm up a long hill in Wales, it went with an extremely loud bang, and definitely could not be fixed at the side of the road.
...
Thanks again for the info.,
Scott.
Stoney Peak BMW Service
Victoria, BC. Canada
BMW Classic and Vintage Motorcycle Service and Restoration
service@stoneypeak.com
- miller6997
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Re: 1969 R69S US Crank Balancer (damper)
'67 R69S
'13 F800GT
Altadena, California
Re: 1969 R69S US Crank Balancer (damper)
When I bought the bike, the crank damper was in a saddle bag. I re-installed it and found the engine would rev high with less vibration. The rubber insert ring would eventually deteriorate and require replacement. At some point, IIRC (this was in the early '80s), the rings were made somewhat harder and they would last longer.
I'm wondering if replacements are available. Any information is much appreciated!
- schrader7032
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Re: 1969 R69S US Crank Balancer (damper)
http://www.benchmarkworks.com/
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
Re: 1969 R69S US Crank Balancer (damper)
I have a long project ahead of me. I've reached out to Vech about cleaning the oil slingers for starters. The bike was running well when I put it in storage, but I have no actual idea of the total mileage since the last service.
Steve
Re: 1969 R69S US Crank Balancer (damper)
1. I ride mine pretty hard - should I install the torshion dampner if possible?
2. Will I need to replace my chest cover with one that has a bulge (‘65-on) ?
Thanks, guys!
Coconut Grove, FL
- schrader7032
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Re: 1969 R69S US Crank Balancer (damper)
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
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