carb tuning 2k-6k rpm

matthew patton pattonme at
Sat Sep 5 22:06:16 PDT 2009

I have minor backfiring at idle and closed throttle. it used to be a LOT worse but I richened up the idle circuit to 3 turns on 1 step richer needle jets (15's??), and it's decreased noticibly. but I'm rich (f/a of 11.7 at 3200rpm to 12.09 at 5900rpm) after which at 6000 rpm I hit 12.2 (theoretically max power) and make a slow rise to 13.5 at 8000 rpm and then a slow decline to 12.8 at 10,000 rpm.

so mains seem to be decent. it's the early circuit that's off. i'm thinking of 1/4 turn in on idle mixture and 1/2 notch lower on the needle (factory pro 10 kit). that sound about right?


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