The primary engine type used by modelers today is a single cylinder, two (2) cycle, air cooled reciprocating engine that uses a glow plug ignition and a special fuel mixture of methanol, nitromethane, and castor oil. Most of the components of the engine are made of cast, forged, or machined aluminum. The power that can be achieved from these small engines is phenomenal and can vary greatly from one design to another. A typical inexpensive .40 size engine can produce 1.1 horsepower at 11,500 RPM. The same size racing engine can produce 2.4 horsepower at 20,000 RPM. All of these engines are the same in their basic components.

Air bleed screw - Screw for adjusting the amount of air allowed to bleed into the carburetor during idle

Backplate - Cover over the rear of the crankcase

Carburetor - Device which mixes fuel and air and controls the amount of mixture entering the engine

Crankcase - Main body of the engine

Cylinder - The section of the crankcase where combustion takes place

Glow plug - Device which provides heat for ignition of the air/fuel mixture

Head - The component which forms the end of the compression chamber of the engine

Mounting lug - The section of the crankcase used to mount the engine to the airplane

Muffler - The device which reduces the noise level of the engine

Needle valve - The device used to adjust the air/fuel mixture

Prop shaft - The main crankshaft which transfers the power of the engine to the propeller

Throttle stop screw - Screw for setting the lower limit of the throttle movement

The design of the engine affects its power output, reliability, and longevity. The prop shaft is supported by bushings or bearings. Wear takes place between the piston and cylinder wall and the prop shaft and bushings or bearings. Most engines on the market today are classified as ABC meaning the they have an aluminum piston and chrome plated bronze cylinder sleeve. This combination normally produces an engine that yields many hours of trouble free operation if properly maintained. Those engines that have ball bearings for supporting the prop shaft normally produce about 25% more power and last much longer.

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