I am rebuilding a 1972 norton commando combat eng.# 204091, after refitting the bottom end with super blend mains and bolting the cases together, there's no end play, [should be 10 to 24 thou.] I even re heated the cases,dropped the new bearings back out to check for anything strange,re fitted them and they bottomed out evenly, still no end play.The crank turns freely and is in good shape and the inner races bottomed out on the crank.ANY IDEAS? Note: this model used roller or barell style bearings on both sides and not a ball bearing on one side like previously.???
#1. "RE: crank shaft endplay" In response to Reply # 0
I think that I have experienced this as well. I have consistently found with new "Superblends" that I can set the end-float whilst the cases are still hot from dropping in the bearings but that it seems to disappear as the cases cool down.
After 1000 miles or so, it then becomes possible to feel end-float again by grasping the crank nose.
My suspicion is that this is caused by using bearing-fit and that this produces a slight degree of interference fit within the bearing as everything cools down. This appears to combine with the surface-ground finish on the bearing components to give the impression that there is no end-float.
If it's any reassurance, I have never found any sign of damage on the bearing tracks so presumably it is not detrimental. I have only ever replaced "Superblends" as a precaution (usually after yet another cam & followers job, but that's another story !)
If your motor is not yet fully assembled, I would suggest a gentle oven job to see if there is any sign of movement when hot.
If the crank and cases belong to each other and the bearings are properly fitted to crank and cases, the only other possibilities are oversized bearings (Never heard of that) or that the crank cheeks are not fully assembled or are not sitting squarely if you dismantled it to clean the sludge trap (always a good idea).
I hope these thoughts help.
#2. "RE: crank shaft endplay" In response to Reply # 0 Fri Jul-07-06 09:37 AM by dynodave
Are you going in with a pinch bar/big screwdriver to "push" the crank side to side between the crank cheek and the cases?
If tight, they will not seem to gently slide by the pull/push on the crank drive end. Yet the crank will seem to rotate OK....However,I would suggest investigating, since that condition is undesirable.
Did you use the correct bearing to obtain the correct running clearances on the inner race? generic industrial bearings may be to tight. Sorry I don't have the proper bearing # suffix on hand.