it been years since I used one but I'm thinking your talking about a spring start, reed valve, .049?

it's usually about 2.5 turns out on the needle and they like about 30% nitro. The thing is getting the needle right and a real good wined on the starter. Give it little prime by putting some fuel in the exhaust slits. If ya flood it unscrew the head and pour out the fuel.
Every cox 049 I ever had was a total pita to start the first couple times while trying to find the right needle setting. Ya just gotta be patient with em. Once ya get them going there almost bullet proof.