daveh:
For someone not familiar with these little engines, you sure asked the right questions!
FWIW, I'm not too familiar either, I'm learning as I go.
The engine was originally roller on the drive side , Ball on the timing.
I just put a brass caged roller bearing in place of the ball bearing.
Crank endplay will be controlled by shims only. .003 play dry will give me plenty of freedom
(after I assemble the cases with loctite 518 flange seal) without being too much.
I set the endfloat to its minimum of 3 thou to of course reduce the effect of a crank moving from side to side,
in 3 thou it can't pickup much speed, and it's inertia that accounts for banging the bearings into submission.
I used a new Alpha B26 crankpin (Big end bearing). It has 12 full rollers (unlike the Stock 24 smaller/split rollers)
and an alloy cage.
Rod to flywheel clearance is 12 thousandths (.006 per side) which is really determined by the machining of the
flywheels and crank pin, I didn't have any control of that.
From what I have read, there is plenty of clearance to insure proper big end oiling.