hi, my name is logan, i have a offroad mower, which i have many question for but will ask those later

i am building a homade go kart, and am using a B&S 6.5 hp engine, and i will use an 5 speed riding mower rear transmission

i would love to boost the power of this engine, does any body know of a racing crab i can get for this engine?
and i would also maybe like to remove the governor, if so, how do i do that? and if i do, are there any internal modification i should make to make it safer?
and last question about it, does anybody know of any performance kits for this? like maybe a kit that comes with aftermarket air filter, or exaughst and maybe pistons or camshaft?

thanks so much and i can't wait to hear your replies!

-logan