Hi. Our 12 hp kohler has developed a symptom. Once in a while it would stall while mowing, as if you turned off the key. It would immediately start back up and often run for an hour or more until we finished mowing. It has now began stalling out after about 2 minutes of run time. Its not the gas cap vent, and the condenser was changed a few years ago. When it stalls the rpms go down then it dies. No chugging. I took off air cleaner to see if spraying either kept it going when it was stalling but to no avail so I think its spark related?