There are a couple stockers on eBay, but MAN are they trashed!!!!! And they want TOP DOLLAR!!!!! I was considering using a universal one myself. FMF MegaMax, FMF Q4, FMF the "Q" FMF PowerCore 4 "Q", SuperTrapp universal, Or perhaps one for a CRF230F or TT-R230.

That's news to me J. My old machinist friend (who's been doing this stuff LONG before I was born) bored it for me. He always follows Wiseco specs for clearance. He did the crank too. Always the good stuff.