So that it doesn't get buried in the SIR discussion thread (which is now a discussion of limiting engine years), I'm starting this one so we can discuss it separately and put it to bed.
I think this one is easy so I'll take a crack at it.
Where "x" = a given volume of imports or sales, based on what Jon Jeffords digs up. Maybe Hasty Horn has some input.
The only engines permitted must come from a motorcycle model that is street certified in the United States and available through US retail dealers. That model must have achieved a minimum sales (or import) volume of x for the specific year engine used.
As I interpret this, buying an engine from a Canadian source would be permitted because it's probable that the motorcycle in question, while sold in Canada, is street certified and available in the US.
I think it's important that the sales or import volume is for the specific model year to prevent an insider from procuring a 2010 prototype (could happen... ).
Commence to criticizin'.