is it the stock a12 carb or the stock a15 carb?
very important as the a15 carb will have an idle solenoid which cuts fuel to the idle circuit when the engine is stopped.the idle solenoid is the hexagonal bit sticking out of the carb just ahead of the pump jet plunger & has (should have) a wire with a male bullet connection on it.if it's there & not connected,find a 12 v power source controlled by the igniton & connect the solenoid to it.this is just the most
obvious thing to look for,as i've had sunny's do this to me a couple of times when the fuse blows controlling the solenoid.it'll run but not idle.