Check the gap between the magneto and flywheel, I believe there is a spec for it, but I am unsure as to what it is.

Ask if he used the woodruff key in the crank, if he removed the flywheel during the magneto replacement.

A carb kit is about $15, and simple to put on. Could easily suffer from a dead diaphragm if there is ethanol in the fuel.

~Nate

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95 Honda Shadow ACE 1100.
1999 Plymouth Neon Expresso. 2.4 swap, 10.5 to 1 comp, big cams. Autocross time attack vehicle!
2012 Escape, 'hunter" (5 sp 4cyl)