I just remedied this issue with my Carter YF788 on a 235 engine in ’53 truck. All summer, its been running way too rich, lots of black smoke on startup and idling, flooding, hard to start after driving, idle fluctuating, large sooty deposits out the exhaust, occasional hiccup, terrible mileage, etc.
After disassembly, I found the needle valve assembly did not leak, the float was ok, and the accelerator pump did not have cracks or holes. After comparing the new kit parts to the old, the big difference I found was the pliability of the rubber of the accelerator pump. Obviously the years and occasional ethanol use had hardened the rubber enough to cause it to malfunction. I meticulously cleaned every part and orifice of the carb, installed the new kit, re-set the float to spec, and changed the fuel filter. The truck fired right up, no more smoke, idled perfectly, runs and performs better than it ever has.
BTW, Mike’s Carburetor on YouTube has an excellent series on Carter YF carburetors, troubleshooting, disassembly, adjustment, repairs, etc.
