I was used to a single cylinder Sears riding lawnmower for years until the single cylinder Kohler engine split in two, two years ago. Looked all around and decided after research to get another Sears but with the newer twin cylinder Kohler engine - power steering, hydrostatic, canopy - nice little rig. All was good up for awhile although it never seemed to be more powerful than my older, slightly smaller single engine job. Then last week it started cutting out and the only way I got the grass cut was to back the throttle down slightly - like the cable was out of adjustment and slightly choking it. Since I had 45 days warranty left decided to just let a Sears guy come out and deal with it. Well, he fixed another little minor issue and then got on to the motor and pulled the plugs out of it first thing. He called me over and said I think I found your problem - one plug came out in two pieces, broken through the insulator. He showed it to me and remarked he's not sure it ever fired because the portion in the cylinder was still silver and spotlessly clean as compared to the typical black/gray of the good one. He thought it was probably broken in shipping or assembly in the tractor.

He replaced the plug, fired it up and took it for a spin around the yard with the mower engaged and it never missed a beat. So apparently I've spent two years mowing with a twin cylinder engine mower with only one cylinder working and I was completely oblivious to it. So much for my mechanical acumen. Still not sure how it managed to run pretty smoothly all that time until a week ago considering the plug look virtually unfired. Now I'm excited about getting out and mowing again - this sucker should have some real cutting power now. Whoo-hoo!