Small Engines (Lawn Mowers, etc.): motor replacement, cub cadet 782, spark plug wire

Question
Hello, I have a Cub Cadet 1340, It had a Koler Command 12.5hp engine on it. I picked up a IH Cub Cadet 782, with a 17hp Koler. I put the 17hp in the 1340. I'm having problems keeping it running, with a jumper wire going from the coil to the pto switch, I can get it to run, but only with the switch turned all the way, with the starter turning over. Once I let off the switch to the run position it shuts off. Does the coil have to have a constant hot running into it? The 1340 wiring had a magnito. 782 has a coil, any suggestions how to fix this?
                                  thanks

Answer
If the engine has an old, automotive style coil with two wires plus the spark plug wire then it needs to be hot when the key is turned on.

If you look at the coil, you should see a "+" sign on one of the posts.

Can you attach a picture of the coil?
Eric