15 hp Craftsman Kohler not running on hill

Welcome!

So to make things clear, it only does this when you go up hill and not anytime else?

If so, it sounds like something fuel related. Is it fuel injected or carbureted? I would check for fuel flow and to make sure there is enough fuel in the tank.

Seems like there was someone her that was having a problem going up hill but not downhill or on level ground and it turned out a wire shorting to ground.

Perhaps a wire worn through rubbing a moving part like the steering column or shaft on one of the pedals but only makes a solid connection to ground with the help of gravity and a hill.

Just a thought..

Location of safty switch under the seat? Personal wieght shift?