With O.S. Max engines, we have never seen an intact ball bearing assembly with a ball missing. If balls were missing, the ball retainer and other internal engine parts have been damaged.

If a ball is destroyed for some reason, usually the rest of the bearing is destroyed, also. It would also be difficult for most front bearings to have a ball "pop" out because of the dirt shield and the drive washer in front of it, and the crankshaft and case behind it.

With non-ringed engines, you must replace the piston and cylinder liner as a set. That's the only way they are sold.