TWO STROKE AND FOUR STROKE ENGINES

The great majority of our engines are two strokes. This means that if we start with the piston at the top of the cylinder (closest to the cylinder head) and it moves as far as it can downwards then it has completed one stroke. When it then returns to the top (the starting point) it has then completed another stroke making two strokes to return to the original position. But because the fuel is ignited every time the piston gets to the top we call it a two stroke engine.

Another type of engine is known as a four stroke and these operate exactly the same as a car engine with valves, camshafts and pushrods.To simplify their operation consider that the piston is at the top and the fuel/air mixture has just ignited. The piston is pushed down to the bottom giving the power stroke (stroke number 1). The piston then travels up pushing the exhaust out (stroke number 2). As it goes back down again it draws the fresh fuel/air mixture into the cylinder (stroke number 3). Then it goes back to the top thus compressing the mixture ready to be ignited (stroke number 4). Then the cycles repeat.

Four stroke engines are more suited to the experienced modeller because of their complexity and need for periodic maintenance such as setting tappet clearances and possibly valve regrinding.

Two stroke engines on the other hand are marvels of simplicity. They only have the bare essentials that are required for them to operate and yet believe it or not, in their more highly tuned versions, they are THE most powerful engines in the world for their size. Not even the best of the supercharged, nitro methane fuelled drag car engines even approach them. Consider that a 10 litre drag car engine would have to produce 9000 horse power to equal the best of our engines!!! Even what we consider to be a sports engine has as much power for its size as a Formula 1 car.

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Prop Balancing
Glow plugs
Fuels
Running in a new motor
How long will an engine last?
Setting the mixture
Setting the idle mixture