I have a 1976 GL1000, which runs very badly below 4000 rpm, I have found that the two front cylinders do not fire and be effective until the engine reaches approx 4000 rpm. I have changed both head gaskets, ground in all valves, checked all clearences, fitted new plugs, points, and condensors, checked all wiring including swapping the coils around. fitted new cambelts, cheked the valve timing both by alingement marks, and with a dti gauge. removed and cleaned the carbs,ballanced the carbs. my best guess is that its a fuel problem. any advice would be much appreciated its beat me!