the correct answer is: "Every two revs per cyl. for a 4 stroke. Every rev for a 2 stroke. I think."
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Every 2 revs. for a 4 stroke?? I'm not sure I understand what you mean. If you mean the spark plug firing, then yes, a 4 stroke fires every other rev., But only one of those strokes is an exhaust stroke.
There are "4 strokes" and only one of them is an exhaust stroke.
* Intake stroke
* Compression stroke
* Combustion stroke
* Exhaust stroke