I was forced to screw around with prime movers including gasoline for many years in the high sierra. Even at 11,200 feet I failed to notice a significant improvement in power by rejetting and at the time I had an assortment of .045" jets and a number drill set. I tried decreasing orifice size until the engines quit running.
Perhaps for long service times, Robert at Honda's advice is sound. Reduce combustion chamber deposits, plug fouling and oil dilution.
But to gain power - I remain thoroughly unimpressed.
SPARK TIMING on the other hand is another subject entirely. Some engines like Wisconsin and 4-cyl Onan's, saw readjustment of initial spark timing eight to ten degrees BTDC.
Your mileage may vary...
