There we go. Aluminum flywheels will go BOOM very fast. Cast iron? A few RPMs after. Get a billet to be on the safe side. Billet is not melted and molded, but cut into shape from a solid block of aluminum. Look for ARC or Clements flywheels.
3HP flywheels are cast iron too. Many people sell these on eBay.
I'd get a cheap performance cam, stainless steel valves, dual valve springs, custom keepers and retainers, hardened billet lifters, tru seal head gasket, 4HP high compression head, billet flywheel, billet connecting rod, ect...
Check out jr.dragster's 5HP. Decked to the maximum, and a monster. (Monster is a understatement)
ok guys the kart bug bit and bit hard. i got this for the kid and now its my play toy. i know some of u guys have swaped out the old 5 hp briggs fly wheel out for the 3hp one now can the flywheel come off a push mower or do i need to find a old 3hp gokart motor for my fly wheel. right now the motor is mostly stock beside milled head stright piped soon a cam will be bought. and the gov removed.right now with a 12-72 sprockets i can smoke the tires with eazz.with out holding your foot down.