Actually Sandking raises a good point, with the bike geared to max out at say 160-170 km / hour the torque and power may very well be competitve, and a lot of fun.

Even the CRF450 geared for road racing feels like a limp biscuit. They feel very slow but still seem to hustle around bloody quick, actually a bit boring until you get in the groove properly.

Your project geared down for the kart / supermoto tracks may very well have enough grunt to be competitve.

As i mentioned, the engines weigh the same so whilst there is no advantage, there is also no disadvantage!

Good luck.

Mark