The engine is a 2 Horse Briggs model 62502, which is a 6 cubic inch engine. I welded double lobes on the camshaft, so that it intakes compressed air inthru the existing exhaust port, usinf the 1/2" pipe thread to hold the air line. The original inlet port is now used for exhausting the used air.
The 7 gallon air tank starts out at 125psi, but doesn't last very long, since it is only 1.1 cubic feet of volume. This means that I have about 8 cubic feet of air at 125psi. The engine will run down to about 10 psi, but can't power the gokart at that low of a pressure.
I discovered a problem thatlowers the power, and uses more air the inlet valve blows off the seat at only 80psi :( So this wastes any pressure higher than that, right out the exhaust valve. I am correcting this problem now!