Mower ran fine 1 week ago. Over the weekend it started and ran fine for about 5 minutes then it started to surge and then stall. Would start right back up and as long as I did not try to move the mower it would run fine. As soon as I tried to move it whether it was on the sidewalk or in the grass it would start to surge and then stall. After about 10 attempts I gave up. I figured it was a fuel problem. I'm using fresh fuel that was just purchased and I cleaned the vent holes in the cap. No help. Changed plug and cleaned carb. No help. Changed carb and magneto. No help. As a last resort I pulled flywheel and changed key and now I've lost spark and mower will not start. I have no idea where to start looking for my "lost" spark or why this motor continues to surge and then stall. I am in need of some help.