
Interesting article about R69s damper
Only the first page is interesting

Interesting article about R69s damper
Others have researched the issue more fully, and as I recall, unless you are consistently riding at 80+ MPH, you are not in the RPM range where the dampener adds any real effect.
The crank failure mentioned in the article could have also been due to other issues.
Interesting article about R69s damper
http://www.sandv.com/downloads/0809lang.pdf