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Join Date: Jul 2006
Location: Kennett Square, PA
Your battery should be reading 13.5 - 14.5 V once you rev up above 2500 rpm. If you have a new stator and r/r, that's probably where your reading are and that's likely not the culprit anyway.
Particularly in light of the backfire, it's possible you dumped some crud out of the petcock that caused a fuel flow problem. Did you clean the carbs when you had the engine out? Use any Seafoam or other cleaning agent?