exhaust turning red hot and trouble idling

[TheStoot]

My mechanic is having issues with a rough idle. It only idles smooth when he keeps his finger pressed on the round plate under the air intake and also the exhaust got red hot at the same time. Ideas as to where he should start looking?

[David T]

Your fuel plunger is stuck. You have to take the mixture unit out and clean the plunger so it slides easily. Do NOT damage the surfaces, they are finely machined so don't go at it with a plier.