For me it doesn’t have to be American made it just has to be well supported in the US. Purpose built is nice but with all the stuff that’s available to adapt a Honda it’s far from a jury rig. For me “what you see is what you get” is a good thing. I’m not interested in chasing the latest greatest Italian engine every year.
4 strokes? I love them!!!! I have a CRF250 and a 450. Both are torque monsters and just amazing rides. Because production numbers on them are so much higher than anything in karting parts and information are very easy to find. The weight is a down side but not as bad as some might think. I pulled a Pavesi off one kart and replaced it with a CRF 250. The increase was under 18 lbs.