There is a kick start idle gear that rides on the output shaft under the clutch cover. It should always spin free when the engine is rotating. In my experience with them, the cir -clip pops off that retains that gear and they get wadded up behind the clutch gear and it locks the engine up against the kicker gears. Pull the clutch cover and take a look. hopefully the groove for the clip is ok, or you have to split the cases and replace the output shaft.
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