- R50/2 /R50S
- R69 /69S
The /2 crank has no centre bearing - it's like a wet noodle.
The R69 can go more than 1000 rpm faster than a /2 and has the damper in front and a special bearing in the rear to help save the crank.
The vibration damper on the front of the generator, which is the front of the crankshaft, is to counteract the flex of the crank at high rpm.
Whatever flexing the damper does not cancel out, the special rear bearing then absorbs.
This rear main bearing on the R69 is a special spherical bearing to allow the crank to flex at high rpm without damage. Imagine a bearing that allows you to move the shaft up and down as you turn it.