Torque-leg-verter?
Push bike chains and sprockets are designed to be easy to derail as well, for changing gear. Not the greatest characteristic for a kart!
Could it be done? Either attaching the clutch to the output shaft, or via jackshaft. I have in mind a weirdy semi automatic shifter kart, could it work?
Impact gun is good, but this guy has stated he has sh*t all money several times, so it's bone advice guys. As I said before, breaker bar + elbow grease!
You need to use a breaker bar or something, it'll be on REALLY tight.
Trust me, I work mainly on bike engines, and there have been times in the past it's taken 5 of us and a breaker bar to get a clutch bolt off.
WD40 won't work, it isn't seized, just torqued on.
A strap wrench is a tool that has a strap made of a friction-y material that you can tighten onto things like pipes or flywheels to undo them.