I'm doing just such a conversion as we speak. Pictures so far are here:
http://www.diygokarts.com/vb/showthread.php?t=5067. I working on the engine mounting today.
It will be considerably slower than a Kart if you use the original drive arrangement. I'm speeding mine up about 25% by changing the pulley sizes on the crankshaft and transaxle input shaft. After I get it together enough to see how that works out, I may remove the governor from the engine which will add quite a bit of speed as well.
I built a frame for it rather than use the tractor chassis. The main reason is to get the center of gravity down so it's more stable, and also stretched the wheelbase out a bit.
I going by-guess and by-gosh on the engineering, just mocking stuff up, squinting past the end of my thumb and saying, "Yeah, that looks about right..."
If you want more speed, either ditch the transaxle or just use it as a right angle gearbox and use the output to drive a jackshaft. That gives you a LOT more choices in gearing.
I expect after my grandson gets a few laps on this rig, he'll be hollerin' for more speed and I'll wind up doing the same thing in the Spring. (Don't get a lot of karting done in Maine in the Wintah...)
