Try neutral with the throttle full and about eight drops. In a few seconds smoke builds up and then move the engine.
The holes have to be cleared too to get air into the chamber.
Pulll something to make the engine work like lighted passenger cars.
Looked at the other thread on the piston. The unit hangs out front. The resistor has two connections one from the center roller. The other to the chassis. I would replace the second with a wire directly to the common side of the reverse unit. where the soldered wire from the coil is and the lever touches.
Quote: One cure that I'm going to try is drop the voltage to the motor.
Use two strings of 3A silicon diodes, about 5 in each direction should do the trick. These are connected in series with the motor. This will require greater voltage on the track to get the same speed out of the motor, and the smoke unit will get the higher direct track voltage.