On a throttle equipped R/C engine there are 2 settings to "tune". At wide open throttle you'll adjust the high speed needle valve to get the correct ratio of fuel to air going into the combustion chamber. When you open the needle valve you'll allow more fuel per given unit of air to get burned. The engine will slow down from it's sceaming high pitched peak and start to blubber. Too lean and the engine will keep the high pitched scream but slow and die.

Don't even worry about the 2nd setting - the low speed idle until you are comfortable in adjusting the high speed needle correctly.

Our model engines are cooled by air AND the fuel which contains a certain ratio of oil - 16, 18, 20, 25% or so. You'll never see reputable fuel sold with less than 16% oil so the markings on the container of 5%, 10% and 15% don't pertain to the oil content but to the nitro methane content.

A rich mixture is generally easier on the engine as it allows it to run cooler. The older engines with iron pistons and steel cylinders required a long break in of careful running on a rich mixture. Modern ABC type metalurgy needs to be brought up to operating temperature fairly quickly as they are fitted extra tight when cold. As soon it is started it needs to be adjusted to near it's peak setting, then can be backed off slightly.

Any new engine needs help by... Running a mild fuel with ample oil content; running a slightly smaller propellor to decrease the load on the engine and; running in a rich or nearly rich setting.

Follow the engine manufacturer's instructions. A good engine will run you $100 or better - depending on the size. Learn to "listen" to it and care for it. It will give many years of great service. A poorly treated engine will live a very short life and never develop it's potential.

Harry Higley's yellow book, "All About Engines" found in hobby shops offers great information on model airplane engines.