OK, newb here just an '86 250R complete less engine/trans for free. Looked for a stock replacement and there's no way I'm dropping $500+, if I'm dropping that much it will be into my AC 650H1 not a "freebee" quad. I have no "loyalty" to any particular manuf so I'm looking at all of them for a 250-500cc engine. Has anyone tried transplanting anything else into one of these? Got the welder, plasma, lathe, mill and ability to just about anything. Is there another engine that fits in easier than others? What about going air cooled rather than the water cooled? I'm not looking for a race machine, just a play toy. My property borders National Forest so I have 65,000 acres to play in and would like something a bit faster than the AC 650 H1's top end of 40MPH.