464 lumber mill that turns planks into logs

If the string is jumping off the pulley, then either your voltage is set too high, or your string tension is too low.

Lionel used the string motor on a number of accessories including:
Saw Mill
Dispatching board
News Stand
Culvert loader and unloader
Forklift platform
175 rocket launcher
264 Forklift platform
3434 aquarium car
3444 Cop and Hobo car

I may have missed a few.
Regardless, once the mechanism is properly adjusted the string motors work fairly well.

If your sawmill is turning planks into logs, you may have a real money maker there.  I always thought it was the other way around, but who knows these days. Modify it a bit more so it turns planks into fifty dollar bills.  Now you've got something.

 I thought the same thing as William 1.  It's probably giving you trouble because it is working backwards. 

Dennis

Have you tried taking an extra bite of string around the pulley? That works in real life, on some construction winches.

Make sure you have the string going the right way around the pulley.

See this thread for a couple of pictures of the string motor on a 334 Dispatch station. It is not identical to the setup on a 464 Saw Mill, but it is close. The attachment point for the tension spring is different. The string is blurry because the motor was running when I took the picture.

I recommend against any lubrication of the pulley or string. They need to be clean and dry. If you replace the line, it needs to be unwaxed.

It might also help to read the original Lionel factory service manual pages on the 464

Interesting... it has been the most reliable accessory I have going back to 1993 on the floor.  Voltage is key.  You don't need too much.

Jon