I have an old Craftsman LT4000 that I just use to tow a little cart to haul things around the pasture and yard. It doesn't have a deck. It is model #917.255450. The engine is a Kohler 14hp. It just decided it was going to not start the other day. Some time before I bought a second similar mower with a 14.4 hp engine that ran beautifully but the gearbox was locked up. The mower repair places are just swamped now so I went ahead and switched the carbs around and it ran perfect (actually better) except that when I idled down it backfired and ran a bit rough. If I keep the idle up it runs like a new one. What do I need to do. The spark is great. Thanks for any help. Kenny
