A minibike guy, huh!?!?!
I have 5 minibikes right now but only one that's ridable, I just had it out last night for my cool down lap after mowing. You can't beat the harbor freight motors really for the price, I have one that I pulled off my minibike to put on my drift trike when I get it done.
Head over to http://www.oldminibikes.com and ask over there, tell them hemigremmy sent you.
They are a good group of folks over there and there is a More Than Two Wheels section for karts and old school trikes and stuff.