ORIGINAL: -EXTRA-
250CC 2-stroke dirt bike engine (like the YZ250, CR250, RM250) yeah would do good, but not a street bike 250 it would be under powered.
Though most shifter karts run 125cc engines, I like fast cars with a high wow factor.
If it was me I''''''''d drop a CRF450 engine with a 498 or 502 stroker kit in one, with a FMF mega bomp header, or a supercharged GSXR 750
a 250cc street bike engine would not be underpowered for a go cart...i say go for the 250cc like a ninja and slap it on there i say that because it''''s the easiest thing i can think of to make a shifter cart since everything is already on there all you got to do is make the mount''''s and mount it..
Street bike engines make HP but not torque, they make their power up high when dirt bike engines make theiyr peak power around 6,000rpm - 9,000rpm and a street bike make its peak power around 8,000rpm - 12,000rpm most street bikes are 4-cylinder engines, so they won''t make a lot of torque.