Motorcycle Repair: Crank bearing noise?, honda cb160, cmsnl

Question
Bill,
My 1966 Cb160 crank bearings spin nicely but some are growly, is this a consern? I dont see any rust on any bearings. Is changing the bearings anything I can do?
Regards,
  Bruce

Answer
Brewster,  only the end bearings were available as separate parts and they may be impossible to find new. If bearings get metal caught in the races, it will rough up the balls/rollers and races, causing noises. Yes, this can be cause for concern, especially with a crankshaft turning 10,000 rpm.

http://www.cmsnl.com/honda-cb160-sport-160-usa_model1004/partslist/E++02.html

Bill Silver