First time poster....pretty cool site. My father just gave me a John Deere STX46 5 speed with a Kohler Command CV 15 S. Before he gave it to me he beefed up the front end, had the engine looked over at the local JD dealer, and had it running better than it had for some time. When he loaded it on the truck it ran like a dream. After a 3 hour drive it ran horrible. We could barely get it off the truck. It started, but then acted like it just didn't want to get going. If we put the throttle in choke or in a high throttle position it would stall out. Same thing on the low end. We checked the spark plug and it was OK. I'm definitely not a mower mechanic, but not afraid to tinker. I took it to a friend and he opened up the carb. and found a bit of dirt, but not much. He also noticed that I had gas in the oil. When he took the throttle controls off and messed around with it a bit it started running good again when he was controlling it manually. After putting it back together it runs crappy again. A local JD dealer here told me to change the oil and put some STP gas treatment in it then let it run for 45 minutes. After that check the oil and change it again. He said he thought that would get it for sure....it didn't. Now I can't even get it started. Any Suggestions???