SuziQ
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SuzukiSavage.com Rocks!
Posts: 56
Oshawa, Ontario Canada
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The four strokes in a cycle; intake, compression, power and exhaust require 720 degrees of crankshaft rotation (2 revolutions) to complete. The single cylinder having no other cylinders to share ignition with fires the spark plug at the top of the compression stroke and then again after a full revolution at the top of the exhaust stroke where there is no combustion and the spark is wasted in this sequence but it fires easily as their is no compression to fire against. Twin cylinders sharing a single two tower ignition coil also fire a wasted spark as both plugs fire simultaneously, again one on it's compression stroke and the other on it's exhaust stroke. Single cylinder engines are more difficult to start, the engine crankshaft must go through 2 complete revolutions for a firing event to occur and are often designed with a timed decompression system where a lever opens an exhaust valve while the starter motor is running, relieving compression against the starter motor until ingnition is sequenced.
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