i found this for you

The easiest way to increase your engine's horsepower is simply to tune it properly. If your engine's fuel/air mixture is too rich (too much fuel), it won't make full power and you will use up your fuel very quickly. An engine that is being run too lean won't have enough fuel to burn, and that will cause it to run erratically. Start the engine and run your vehicle around to get the engine up to running temperature. Adjust the high-speed needle first. You're aiming to tune the engine so that its operating temperature is somewhere around 230 degrees. When adjusting the high- and low-speed needles, alter them by only 1/16 turn at a time until you have the engine running properly.


from this site:
http://www.storacingproducts.com/rc-...horsepower.htm