When I was a senior in high school, I built a wooden go cart for my little brother — had a Lauson flathead engine, drove the right rear wheel with a Rube Goldberg centrifugal clutch/v-belt drive, and it went maybe 15 mph. Brake was a 2x4 that rubbed on the left rear wheel! Brake and v-belt had to be replaced often!
In order for us to outrun the local rich kid and his custom made tube FRamed go cart (this was about 1958-59 time FRame — things were a little more primitive then), I tuned my brother’s cart to use my model airplane fuel, which was 20% nitro, IIRC.
Went like the hammers of hell for a couple of miles and then threw the rod out of the side of the crankcase (awesome explosion!), just as my brother was outrunning the local rich kid! Nitro will do that, we found out — apparently it allowed the engine to over-rev & toss the rod.
We bought a used B&S engine so we could stay in the game, and decided not to use model airplane fuel again! Since one lap around our block was one mile, that was the track we raced on. In retrospect, it was probably very dangerous, but, JEEZ, was it fun!
Kids probably can’t build stuff like that nowadays — LIEberals probably have rules against having fun in your own neighborhood!
I thought of my kid brother’s “go-cart” when I read your post about the golf cart & dead batteries. Your buddy will need more than a 5hp B&S engine though. Those carts are heavy! Let me know how the project turns out, will you please?
The governor should keep it from over-revving. I'd say it probably broke the piston from detonation. With nothing to hold the rod in place, it fell out of the cylinder and got pushed out the side of the crankcase.
Nitro (nitromethanol) actually has less energy per pound than gasoline. A pound of nitro has about half the energy as a pound of gas. But gasoline mixes with air at 16:1. Nitro mixes with air at 4:1. For the same amount of air, you can burn 4x as much nitro, so you can get twice as much energy out of a cylinder charge. In order to make that work, you need to replace the main jets with something substantially larger. If you don't it's going to run lean, and detonate.