Re: timing on a 10 horse johnson
Proper timing is achieved through point gap. If you set the gap on both pointsets to .020" at widest opening, and you have no lateral play in the armature plate, you should be good there. Any lateral slop in that plate relates directly to point gap, throwing the timing off. Is your backfire actually a lean-sneeze? Try adjusting the mixture knobs counter-clockwise to richen the mixture. High speed initial setting should be 3/4 turn open from lightly seated, Low speed 1.5 turns. You may have to remove/re-orient the knobs to turn the proper amount, as they likely can only move 3/4 of a turn with the knobs in place, as they are indexed (you'll see what I mean when you remove one).
Report back on progress...And good luck!
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