mate used to race karts quite seriously. started with 125's and moved up to 250 gearbox in the end.
the 125's were fun but they never really seemed that fast but were ok once they got going, the 250 gearbox on the other hand that was bloody quick.
but he made the mistake of takeing the piss out of the kart my mate less bought just to piss about with just happend twigworth brake bikes and it ended up with an engine that was significantly bigger folled by one that was much bigger
took it on a testing day at pembray and got banned

rear wheels were good for 4 sets of tyers rear slicks would do 6-12 miles