Man I'm lost. Have a Husky ZTR with 25 hp kaw. motor. I have a problem where motor works fine for about 20 or 30 mins. then starts running on one cylinder. I am a mechanic by trade and been working on this stuff for years but this one has got me. I have it narrowed down to an ignition problem. I have adjusted valves cleaned carb. and new plugs. So here is what it is doing. Coil on right cylinder was not firing pulled wire on left cyl. and engine quit. So i reversed the coils and now if i pull right plug engine quits. That's what I expected but what I didn't expect is that now the original bad coil started working on the left cylinder and now the good coil is not firing on left side. This one has got me scratching my head. And to confuse matters even worse if you start mower on one cyl. with left plug wire unhooked it will start on right cyl. but if you plug both wires up and pull left plug wire it will die. I have pulled ground circuit to coils with same results. Any help would be appreciated . thanks.