The fundamental characteristic of 4 stroke otto engine is, the a cylinder generates one pulse (stroke of power) when the crankshaft rotate 2 circles (720 deg), so single cylinder engine has difficulty to drive the bike to higher speed while it need one stroke to exhaust the burnt air and one stroke to breath in fresh air and fuel. the addition of another cylinder alleviate this problem by providing a second pulse to mitigate the lack of power of single cylinder engine. 4 cylinder of more engines provide very smooth power delivery, but they consume more fuel due to addition friction from other additional cylinders.
