Originally Posted by Outrunner
Jim, From my 8 years of drag racing motorcycles and 23 years of MC repair and engine rebuilds, I would only recommend a bushing for the wrist pin end. Like
you stated, "it's a hammer on top of the piston". The upper wrist pin end of
most engines has very little rotation as it travels up and down. This puts a
LOT of stress to the same area of the bushing or bearing during its limited
rotation. If one would examine a worn upper rod bushing you would see that
it always wears oblong due to the upper and lower "pounding" it takes.The
roller bearings do no not really allow rotation of the bearing rollers, which
causes early fatigue and failure of the bearings.
That's been my observation and experience from a few years of engine rebuilds.
That is the best description ever of what's going on with these bearing. Too bad the makers don't listen. Thanks.