I have a honda 13hp wanna mod it out, so what are the best cost:power mods.
Im hearing of racing cams and taking out the governor and of course theres exhausts and carberators but whats the best mod for the money?

Google it. The go cart buys do crazy stuff with 13 hp motors. I have one, and the cheap way to get more hp is to upgrade the intake and outake. Take off the muffler and look at what the big mm have for intakes. Again the cart guys go into the high tech stuff

yeah after i posted this i actually found a good place to get some stuff.
what do you have your 13hp on?

nrracing and agk are some good places to start. intake and exhaust. carb. flywheel advancement. some of the lesser cost things. then you can start to get into some money. cams, rods, rockers, bigger valves, milled and ported head. i have a lifan 15hp. carb, intake, exhaust, and flywheel advancement. about 2-250 $ into it. hasnt been dynoed but i am sure she has a few more horses behind her. and the torgue these big blocks have is great!!

De-baffle exhaust, open air filter, jet it, play with governor.

Don't waste your time on that motor. It’s really an 11 hp at max torque. Tricked out maybe 18 hp and still keep it reliable.