Originally Posted By: JetStar
I seem to remember reading or hearing something similar. It was on ball and roller bearing crankshafts. The theory was the oil was so slippery the ball or roller would skid and flatspot as opposed to rolling normally. This has not prevented me from using synthetic in my ball /roller bearing cranked bikes. I like living on the edge.
I've heard about that - years ago. Never actually come across it, though. It was a bulletin from SKF alerted me to the possibility,but I think it's relatively rare.
I did perk up when I read it, as two of my bike engines are ball-bearing crankshafts and got a little bit concerned for about five seconds.
Otoh - I managed to kill one of those crankshaft bearings. On a cold and frosty morning, started up the bike, gave it the normal couple of minutes warming up, pulled the clutch in, knocked it into 1st gear and there was almightly clank noise. The 20w/50 oil I was using was wrong for that morning and the clutch pack had stuck together just a little bit too much, imposing a shock load on the #4 outboard roller bearing.
Funny how, in well over 200,000 miles of courier work, in all sorts of conditons and who knows how many cold starts there was never a trace of a problem, but I hold my hands up - I had planned to drop the oil and put in a 10w/40 that weekend but didn't get around to it.
My fault for that one. I've still got the engine, and another one with a different gear fault, to make one out of the two.