| A piston goes through the intake,
compression, combustion and exhaust strokes every Two (2) revolutions of
the crankshaft. When a single cylinder (Four-Stroke) like a lawn mower
is idling you can hear the pop-pop-pop-pop-pop-pop-pop sound at regular
(steady) intervals. It's the sound of the individual strokes. What you
are actually hearing is the sound of the compressed gases in the cylinder
escaping when the exhaust valve opens. Each "pop" is the sound of the exhaust
valve opening one time. That happens on every other (2nd) revolution of
the crankshaft.
Normally if it's an engine with two cylinders, the pistons are timed so that one fires on one revolution of the crankshaft and the other fires on the next revolution. (One of the two pistons fires on every revolution of the crankshaft) This gives the engine a smooth balanced feeling. To get this type of engine, the crankshaft has two separate crank pins for the connecting rods from the pistons to connect to. The pins are 180 degrees (exactly half way around a circle, since there are 360 degrees in a full circle) apart from each other. The Road Star engine similarly has two pistons but the difference in the Road Star engine is that the crankshaft has only one pin, and both pistons are connected to it (the single pin) through their connecting rods. This combined with the Road Star's unique 48° angle of the "V" arrangement of the cylinders means that the pistons can't fire at even intervals. Instead of one piston firing every 360 degrees, a Road Star engine does this: a piston fires
"Even with a very quiet exhaust system,
the uniqueness in sound is still there." I prefer to say it as: Potato,
Potato, Potato, spoken relatively fast, does quite a good job of defining
how they sound. I don't think ya can get much closer. Say it out loud,
and you'll see what I mean. The Po in Potato being the power.
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