There's a plate on the engine that says "Fuji Heavy Motors". It will give a model #. If that's work away, missing, or you can't otherwise read it - the model # should also be in the casting on the Mag side between the recoil and the case halves. Or you can take a picture, post it here and we'll help.
I assume it's liquid cooled. If it's all bare aluminum you're looking at an 83-90ish engine.
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