I have the LGT2554 with the Kohler motor. It keeps stalling out after about 30 min of running and only stalls when going uphill. It did this to me last summer for about 3-4 mows and then worked fine again for the rest of the summer. It has worked fine this season until now. I can immediately move it to a flat or downhill location and it will start right up and run fine. It is right at the 100 hour mark. Is there any suggestions on what this might be?