My 17.5 hp craftsman lawn tractor was just tuned up with a carburetor rebuild a few weeks ago. Since then I've been having a problem with it dying out on me and then being hard to start. It does run for long periods of time until I get on an upward incline. Sometimes, if I'm fast enough, I can level it out and it will recover and run fine. It acts as though it is being choked down.