How will the CR250 Flywheel affect the 500 though?
simple, take a 250 and a 500 one and have them both spun to see what the balance is at, any one how balances small cranks can do it. If they are differant have the 250 one changed to balance like the 500 one.
As for the later 250 digital units they also have a electric sensor circuit built into then for carb enrichment, left unused It may or may no effect how the unit overall works, that would be a testing issue.
I've run the pre digital 250 CDI box with good results using the 500 stator assembly and coil.
What gets me is unless you are a seriuos MX racer why do you want to tame it down like a 4 stroke? Not sure if most of you know this but most of the HIT is in the pipe design, all 89 and up regardless of make, OEM or afthermarket, have a mild no hard hit kind of power. If you ride a stock well jetted 86 or 87 and the put it into a 90's frame, rejet again to match the new pipe, you will be amazed at how the hit flattens out into more of a smooth pull.
That's why I don't get it, the 500 is for shits and grin factor! it's already tame with a 90's steely or AF, makes no sense to tame it more. you serious MX guy's need a 450, If you don't beleive me take your 500 out and run with 450's in Supermoto trim on a closed course.