I have a Craftsman lawn tractor with the 19hp Briggs twin 42E707. It is loosing power and firing intermittently on the Left side only. This is a single coil design, and has 105, and 110 lbs compression right and left. When power is lost I can smell unburned fuel and the left plug is wet. I installed new plugs and got about 5 hrs service. I did a spark test and noticed that I had no spark on the left until I released the key. Someone in another thread suggested the possibility of a short in the ground wire or a bad diode. The manual that comes with this is poor at best. Where would I find that diode? Any other suggestions?