If you want gobbbbbbbbbbbbbbs of power for cheaper than the built Briggs, do what I did and put a 2 stroke dirt bike motor in it. I put a YZ250 motor in mine and holy fuck, hold on to your diaper cause you'll need it. Some of the guys here are putting 500cc 2 strokes in them. These will do wheelies, gaurinteed. I used to have a vidio of a kart with a GSXR motor on it. I'll see if I can find it again.