XR70 ignition timing question

Hello all-

So I'm putting an XR70 motor back together and have the cam gear and flywheel marks lined up as the manual says, but I'm wondering something. Does the spark plug fire every time the pickup on the flywheel comes around even when the piston is on the exhaust stroke? I know this sounds stupid, but the flywheel goes around twice while the came only goes around once during the complete four stroke cycle. How would the ignition system know when the piston is on the compression stroke as opposed to the exhaust stroke when the module is getting the signal directly from the flywheel? Sorry for such a long post.:confused:

Your ignition system is a electronic CDI Ignition and tells it when to fire on the compression stroke

notice on the flywheel there is a (F) and a (T) the (F) is when it actually fires just before (T) TDC

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