I have an older montgomery ward riding mower with a 38" deck and the 12 hp tecumpsa motor. It was sitting outside for a long time. Anyway I got it running but it doesn't want to run right and the ignition switch won't shut it down. It surges and sometimes it will rev up pretty high and will smooths out but won't throttle down. Any suggestions?

On mine you have to move the deck adjustment lever forward one click to engage it.

Hi,
I moved your posts out on their own since you added it to a 6 year old post. Your machine is made by MTD. Is the engine OHV? Found any numbers on that critter? It sounds like your problem to address is a dirty carb possibly with a sticking throttle shaft.
Peace,
Clarke