1969 R69S US Crank Balancer (damper)

[niall4473]

Hi all, haven't posted on here for a while but felt I had to correct some incorrect statements about this device.
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.

[808Airhead]

I have mine installed and have "revved the piss" out of my R69S and it feels like one of the smoother,if not the smoothest engine at higher rpms of my 4 pre-1967 machines. I check it at service and my "plastic/rubber ring wore out at 12k miles,where the metal ring could spin easily and had some "play" in it.

[sblaylock]

...
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 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.

Thanks again for the info.,
Scott.

[miller6997]

The damper from my '67 has been in the spare parts box for about fifty years. The bike is about to turn over 90,000 miles and there are no signals yet that removing it was a mistake. It's a gently used bike that's never seen a lot of stress, so maybe it's not a good example.

[RootDoc]

I'm starting to gather information and parts for my '67 R69S, which has been in suspended animation of sorts since 1985.
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]

Welcome to the forum! Yes the rubber part of the damper were problematic in the past. But Vech at Benchmark Works ended up with a longer lasting material. MaxBMW recently bought out Benchmark Works and all inventory was transferred to them. You can still use the old website to search for parts...call the number at the top. Part "11230070709 damper rubber 50S 69S"

http://www.benchmarkworks.com/

[RootDoc]

Thanks, Kurt!
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