I completely stripped one then put some soft 18" knoby tires off my off-road go kart on it. It was sweet in the mud, just kept on going like the energizer bunny. Drag racin it was alright except for the fact u cant shift on the fly without throwing the belt off. It did spin the tires on the road though when i dropped the clutch (before the knobys). Im pretty sure you could make one of the chain drive ones (ex: Sears brand) go real fast if you just gave it a solid rear axle off something else and use one of the better front ends.

If you want to go fast just jump on a hydrostatic drive one, our ancient cub cadet which weighs a ton will do atleast 45 or more, past that i get kinda scared... lol

 

Did they use an older style sears? I used a newer one, but the rear end..... um ... um .... flew apart.

 

i made a 12 hp sears rider do 40 just by opening up the intake and taking off everything i could and i put she samllest oseeible pulley on the rear then to some springs off the deck and attached them to the clutch and made so the belt cou,dnt slip and finished it off with 22 inch 4 wheeler tires

 

HHMMMMM,,I have an old sears mower that looks just like the ones you see on espn2. It has a 8 horse briggs that I milled the head way down on, I quite using it because it has so much compression it keeps breaking ropes when I start it, but for limit use ie: going real fast, it may just be the thing to use, I will have to get out the torch and remove some excess metal and change some pullys, I will get out the GPS and give everyone a top speed review when finished,