I know the gas is good because I used it the day before it stopped running. I tried squirting engine started down the carb and into the cylinder head. Normally in the past it would try to start. I checked the spark plug for a spark and noticed that it was giving a weak spark. I cleaned the magneto and the place it contact on the flywheel and then reset the gap using a business card. I then check the plug for a spark. The spark was still weak. I'm beginning to wonder if the magneto is bad, or if there is another contact like a ground that needs to be cleaned. A new magneto costs about $50 and so I'm not looking forward to replace it. Any ideas?