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 Step 1:the intake phase

The rotationalenergy of the motor causes the piston move downward, in the cylinder and this creates lower pressure in the combustion chamber. New air-petrol mixture flows through the opened inlet-valve from the carburettor into the combustion chamber.


Step 2: compression

The inlet-valve  closes. The piston moves upwardly and the mixture in the combustion chamber is thereby compressed.


Step 3: phase of stroke

Just before the piston reaches the top of the stroke the spark-plug ignites the compressed mixture. (see: basic information about the ignition). This combustion produces such a high pressure that the piston is pushed downward again and this produces the power of the motor , I. E. the power stroke.


Step 4: exhaust phase

The rotational energy of the motor urges the piston upwardly again. The exhaust-valve opens and the burned mixture (exhaust fumes) is pushed out of the combustion chamber by the piston and goes through the exhaust system into the air.


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May 29th. 1999