I removed the muffler and tried starting the engine, but it would not fire. I looked the muffler over and did not see any significant carbon build-up. I cleaned it anyway and put it back together. Today, I tried starting it again on the freak chance it would start... it didn't. I removed the armature and cleaned the rust off of it. (I was going to try an armature off a different engine, but the bolt holes were not the same and it would not fit.) So, I figured since I had it off, I might as well clean it before I put it back on. I set the gap at .006" again and put the engine back together. I pressed the primer bulb six times and pulled the cord once, and the engine started! It ran perfect!!! I took it out and mowed the front yard, but before I could finish, the engine began to slow down like it was running out of fuel. I stuck my finger inside the cover and pressed on the throttle to try to keep the engine running, but it died as soon as I pressed on it. I checked the fuel level and it still had half a tank. I pulled the rope again and it started with the first pull. I continued mowing for a while and then it did the same thing again. I lifted up on the handle bar and raised the rear of the mower and the engine immediately sped back up again. I continued mowing and it happened again and again. Each time I was able to keep it running by lifting up on the back of the mower. Finally, I wasn't able to keep it running with the previous method. I rechecked the fuel level and had about a quarter of a tank left. I restarted the engine and it sounded like it was going to stall again. I immediately began pumping the primer bulb and the engine sped up again, but then sounded like it was running out of fuel again. I kept pumping the primer, but couldn't keep it running long enough to finish mowing. It began to rain, so I called it quits, but before I put the mower away, I decided to see if it would start one more time... and it did (one pull starts it every time now), but it would not continue to run.:confused2: