Re: bought a replacement engine and it wont start.
drill out the broken bolts in the other engine and put it on another bike, broken off exhaust studs is an easy fix...............! drill bit and an ease out/broken screw extractor, some new better quality studs and you are off and running like a herd of turtles..........! Weeeeeeeeeeeeeeeeeee!
Seriously, dont trash the other engine over those broken studs, like I said an easy fix.
Hope you get the new one going soon and running great after it's broken in...Good luck