Paul,
The ignition will fit the engine, but there could be a starting issue with the system because of the stator assembly. Is the '81 machine a 250 or an open class engine?
The 250 systems use a 4K stator and the open class engine systems use a 5K stator because they don't spin as fast when kicked over.
If you use the fine wire type spark plugs and gap the spark plug at about .022", it may work.
Penton Racing Products Inc.
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