I have a john deere 05 with a 15 horse kohler. it runs great untill the deck is engaged then it starts cutting out, running rough. I have done all of the normal things to cure a cut out.... new spark plug, new air cleaner, cleaned the carb a dozen times...its clean, new fuel filter, checked fuel pump. checked the deck and belt system for binding, gressed all zerts on the entire mower. I took the kill switch out of the seat and taped it down (temperally). I stoped at the local mower repair shop and they wanted to sell me a new carb. They said that most likely the carb was bad from the alcohol in mordern gas? that carb is 70 bucks and i don't know that will fix it. any ideas guys????