Small Engines (Lawn Mowers, etc.): B&S 21 hp intek, engine model type, carburetor problems

Question
I have 2 year old B&S 21 hp inek engine on my lawn tractor. At the end of the season I was cutting the yard and the motor just start running at a really high rpm but still cut for about ten minutes. I parked it and said I'll check it tomorrow. When I tried to start the engine the motor makes about 1/2 a revolution  and stops. I can manually back the engine up but the next try, the same result. Here's some background on my usage and habits. This riding is used only on a 1/2 acre yard so it take only 20 minutes to cut. I change the oil at the end of each cutting season and in the middle of the season (July), sharpen the blades 2 or 3 times a season. Any ideas?

Answer
Ben
Sounds like you may have carburetor problems,when the engine ran at a high RPM a Throttle spring or a governor spring may have came off.Check around the carburetor to see if any springs are loose or even missing, If I had the engine  model # Type & code I could look it up for you.