Perhaps a partially sheared flywheel key making it slightly
out of time. Loose kill switch wire (rare) or intake valve
not seating properly like IL ENGINE said earlier. I had a
14 HP B&S on a Dynamark that ran lean and would get so
hot you could see the valves running up and down through the
muffler. Or rather the cooler "shadow" of the valves moving up
and down. What a sight at night! I never did get it to stop
running so lean. It would backfire on shut down.
"What a sight at night! I never did get it to stop running so lean. It would backfire on shut down."
Back fire or actually after fire is natural when running lean which is the reason for the carb solenoid in bottom of float bowl. IF you do not have an air leak at carb mounting gaskets then you can drill, enlarge the main carb jet.
