fantastic but not cheap

[Zetomagneto]

Hi Alan, (but worded for others)

I guess it is questionable whether crank wobbling in flywheel or vice versa is the factor!
Unless especially requested and some precision mandrel provided, the crank and flywheel usually balanced together, in which case any dynamic balance within flywheel not likely to be corrected at source.

A colleague recently broke irreplaceable 2 bearing crank in a 4 cyl jowett 10, not long after supposed crack test! With hindsight, excess flywheel runout was suspected...

Crank is normally zero balanced on its own, then add flywheel, then add clutch so each item is in effect individually balanced, thats how one well known vintage race engineer local to me does it.