MTH steamer with fixed drawbar PS2 starts moving at uncontrolled speed

 If the tether was unplugged while it was on the shelf and then plugged back in. I had one that the pin on the engines socket was loose on the circuit board and had to be re soldered. It took off at a fast rate but mostly on corners where there was more strain on the tether. A delicate soldering job that requires a small tip and a steady hand. I believe it's not a uncommon problem on these older engines. 

 The tach reader or missing stripes on the flywheel will have the same symptom. I mentioned the tether because it seemed to run okay before it was stored.

Will check.  I used wrong word. It has a drawbar style connector. I called it a "fixed" tether. It wasn't the right word. 

Tach issues, so you need to check all the possibilities.  Tach gap, bad tape, bad/broken wire at tach, bad drawbar connection, bad tach reader, bad power supply opamp.    G