I'm making mine with a 17 hp
heres a few motor area mockup shots, not fully welded, but more than enough for mockup. its under 50" wide which makes it legal in our local forestry service areas. keep in mind, most of these trannies are design for 20" tires to run at 6-8 mph. I'm going a little over 2 to 1 on my rear axle (25 tooth to 11 tooth) ad going up to23" inch tires.
keep in mind, these transaxles are also used for lawn mower racing, and are pushed beyond 35mph pretty reliably. my area is too hilly for a truely "fast" go kart, but torque and momentum is a definite need. I plan on down gearing the pulley's and opening up the governor from 2000 rpm to about 3000 rpm. I am planning to use a double pulley system from the motor to transaxle to reduce slipping and give me a better shot at having it work out well....
I joined to post this so go easy on me.