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Just stumbled across this on the Mikuni site:-
Backfires Through Carburetor
The information pertains to Harley's specifically but has some relevance to our bikes because they also use a "dual fire" or "wasted spark" system.
Of particular interest is the section on cam design. This would suggest that bikes with high overlap cams, such as early 790's or bikes fitted with aftermarket cams, would be more prone to backfiring through the carbs as the wasted spark actually occurs when the intake valve of that cylinder is partially open. I suspect that this would most likely occur at low RPM's or at cranking speeds.
I have noticed that even my standard 865 with its very low overlap cams has backfired through the carbs a couple of times when cranking, although this was probably due more to a lean condition, and the result is not very nice at all. I guess this is why some bikes have spat the starter idler gear under these circumstances.
Has anybody with high overlap cams fitted to their bike noticed an increased tendency to backfire through the carbs particularly when cranking?
Backfires Through Carburetor
The information pertains to Harley's specifically but has some relevance to our bikes because they also use a "dual fire" or "wasted spark" system.
Of particular interest is the section on cam design. This would suggest that bikes with high overlap cams, such as early 790's or bikes fitted with aftermarket cams, would be more prone to backfiring through the carbs as the wasted spark actually occurs when the intake valve of that cylinder is partially open. I suspect that this would most likely occur at low RPM's or at cranking speeds.
I have noticed that even my standard 865 with its very low overlap cams has backfired through the carbs a couple of times when cranking, although this was probably due more to a lean condition, and the result is not very nice at all. I guess this is why some bikes have spat the starter idler gear under these circumstances.
Has anybody with high overlap cams fitted to their bike noticed an increased tendency to backfire through the carbs particularly when cranking?