The engine is an early model "FOX" .29 or .35 . If you want it to run right, you will need a 10-6 on the .35 and a 9-6 on the .29. They only like to turn 10,000 no matter what prop you use. They are a bushing engine with a cast iron piston and steel sleeve. You will need to run a high oil content fuel that has less than 10% nitro. Buy regular 10% (preferably something like Morgan's Omega and add about 4 oz. caster oil to a gallon. It is best to use the original fox needle valve which is still available. It had two holes in the spray bar. They face front to rear instead off down. Use a non idle bar plug such as the OS #3 or #8 or the Fox std plug.

enjoy

Jim