Adm edit: split from http://www.a7a10.net/forum/index.php/topic,5970.msgRGS-BILL here, for 40 years I fought the one plug sooty, one plug tan or beige, one dry fouled, one not fouled. In my situation the BSA Anti-Biased gasket did no good because that was not the problem at all.. First of all the drilling in the bottom of the float bowl, that allows gas past the jet block into the Pilot Jet system on my 389 carby, was never completed so I was idling on slide height instead of Pilot Jet circuit. Secondly I had one of the alloy cylinder heads that was drilled 1/8 to 3/16's too low on the left side, a BSA factory defect, which is on most all 62 and 63 alloy heads, (check for Induction Port Obstructions on many others also ) When you have this port obstruction the fuel runs into a cliff, so to speak, then the vacuum from the opposite cylinder picks up the fuel for both cylinders, creating a very rich running for that one and fouls the plug. You are always going to have the vacuum in 2 different cylinders pulling, differently, more or less, depending on the valve guide wear, rings sealing etc. By completing the drilling on the passageway to the pilot jet, and grinding 3/16's out of left side intake manifold I cured the ailments that plagued me for 40 years, and finally idled on the pilot jet circuit. Being as all of my riding is in town and on secondary roads ( NO FREEWAYS, TOO MANY CRAZIES !!!! ) I always fouled the right plug , now no longer. You fellas with Iron heads need to check for this malady also, intake manifold fuel obstructions for idling. a little lower than carby venturi is ok, ( .001 or .002 ) too high is never ok. THANKS RGS-BILL
