- Dec 30, 2003
I'm still playing with the lean off idle that's causing some backfire with slightly openned throttle on over run. Closing the idle air mixture screws did help, but the idle is obviously not right at that point. Going down a hill I rev'd the engine then let off. When the backfire started I closed the choke and within about a second the backfire stopped. The choke doesn't effect the idle circuit, so I suspect the lean problem is air leaking past the throttle slide (original 932 Amal stainless sleeved by Gaylord 9 years and 17,000 miles ago). Needle jet and needle are new and the needle is set as high as it can go (bottom notch). The valves were re-conditioned by Rabers in San Jose last year and the engine has 185psi compression both sides ('72 750 combat - new rings on +.020 bore less than 1K miles ago). The carb balance pipe was just replaced in case it was leaking. Pipes are tight with new seals. Ignition timing using a RITA is set at 28 degrees maximum advance. Plugs are tan colored, not white a lean condition. The problem has appeared in the last year - no backfiring for the first 8 years after restoration. Any tuning genius out there can help?