I've recently got my 1978 CB750F back on the road but there seems to be a problem with the pilot screws on the carbs. The bike runs great but its fouling plugs after about 25 miles and when I adjust the pilot screws I get absolutely no RPM response from my digital multimeter or on the main tachometer of the bike.
The bike has brand new D7EA plugs I installed because the D8s were fouling as well. PO installed kerker exhaust, pods, 120 main jets, 35 slow jets, and a Dyna S ignition system but coils are still stock. I'm not sure if the PO has made any other changes to the bike as far as boring or cam changes or anything in the actual engine. The bike will idle fine at 1k rpms but its like the pilot screws have no effect whatsoever on RPMS not even on the digital multimeter. The only time I get any change is if I screw them all the way in, the bike very slightly revs. I keep them at 1 turn out I know factory is 1 and 1/2 but it has D7 plugs, pods, exhaust, and 120 mains which should LEAN the bike out but it appears to be too rich. The pilot screw is on the engine side so IN leans and OUT richens.
The carbs have been completely cleaned, dipped, carb cleaner blown through every orifice. I even just put in 4 new small o-rings and washers on the pilot screws and each one has a spring on it. The fuel is clean and the fuel tank has been re-lined with POR15 and its holding strong. Petcock is clean fuel system is clean the bike seems to run perfect until the plugs are fouled no backfiring no sluggish response at all even though sooty plugs are signs of running too rich. The plugs are gapped correctly. About a week ago even synched the vacuum on the carbs with a vacuum gauge. Another sign of running too rich is the fact its getting horrible gas mileage.