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everyone, thanks for the replies
I'm not going to remove the crank to balance it. Its not worth the hassle.
I may buy a new stock cam and lifters. When I rebuilt the motor I thought I'd hot rod it with a 336 cam and lighten flywheel. The 336 cam had more power but made it unpleasant to ride with a shudder/flat spot at 3k to 4k rpm. I decided that I didn't want a science project so I put the old, original cam and lifters back in and I'm much happier for it.
This time I may buy a new, stock, cam and new lifters. The old cam and lifters were worn but these bikes will RUN and RUN and RUN... even with old, worn out parts. They are really understressed. Just keep changing the oil on time and make sure the valves are adjusted properly.
as an FYI, BMW modded the crank to address the couple on the vertical axis created by the offset pistons. On one counterweight web (I don't remember which one) they drilled two holes in the web, about 1" dia and filled the holes with a slug of tungsten. The tungsten weights are staked so they are not to be removed.
I woudn't try to balance the crankshaft and if some machine shop claimed they could do it I would have a decently long conversation about the tungsten inserts before I handed over my parts.
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