Small Engines (Lawn Mowers, etc.): Magneto, fly wheel, air gap

Question
I have an old Toro 1138 riding lawnmower model 6001469. I've had this mower for about 3 years or so and its been great. At the end of last year I went to go cut the grass for the last time and it would not start. I put it away for the winter and I just got it back out. I've searched the net and narrowed it down to the magneto. I pulled the cover off of the mower, cleaned the magneto (it had some rust on it) and when I put it back on, it amazingly started. I started cutting the grass with it and it is missing out and its backfiring, not loud, but its making a puffing sound. I can ride it for a minute and then it will die. I leave it for a couple of minutes and it starts again. There is some adjustment in the gap between the flywheel and the magneto. Is it possible to get the magneto to close to the fly wheel, or should I re-adjust the spark plug, which is new also.
Thank You

Answer
Use a business card between the mag and the flywheel for the proper setting.
The rust doesn't hurt a thing. It won't hurt to remove it but it wasn't your problem. The flywheel and mag are cast iron and are probably rusty again already.
My guess is that your real problem is probably in the carb. If you put the unit away last year with fuel in the tank and  carb this is definitely your problem.
Clean the carb and reset the mag air gap with a business card and your troubles will be solved.