I have a first model Scag zero turn rider. Kohler engine. Last cut of last year i was in the middle of a pass and she just cut down to half power. Still ran good just half power. Like i had the throttle half way. Just started it back up with new plugs started right up and runs great but same thing only half power. Figured out by feeling how hot the plugs were that im only getting spark on one side. Any suggestions? I really cant afford to take it to the shop, id like to fix it on my own. Any advice would help!! Thanks so much!!