ORIGINAL: rc rock
i think it has a little too much oil and your internal one way bearing will slip, i know this happena with traxxas top fuel but i think that has 18%. i use fuel with 11% oil content and its totally fine.
That is my problem now. My pull starter only turns the engine over a fraction. It's like it isn't grabbing on something. I also use the Traxxas top fuel 20% nitro. Now I know why it's slipping. I will pull the motor out next weekend and clean things up.