Jim -Rosemark Lawn Servicing I've got a John Deere GS30, 36" geardriven walkbehind with a 13hp kohler engine. The engine runs fine at full throttle and has plenty of power. The problem is when not in full throttle the motor will rev up and constantly, and when i push the throttle to the half position it will shut off? The dealer said it needs a tune up? What do u guys think? please respond ASAP!!