Small Engines (Lawn Mowers, etc.): Lawn Mower serges, briggs and stratton, head gasket

Question
Hi John, I have a Briggs and Stratton Lawn Mower engine Model 10A902. Actually says Murray on the front. The Lawn mower startes right up but constantly serges from low RMP to medium RPM. Also smokes when running. I couldn't find any Fuel mixture adjustment screw to adjust. I don't believe that caburator has any. I took the Carburator apart and cleaned all the parts. The gasket seems to be slightly distorted from where the spring presses against it. I don't know if that can be the problem. I emptied the gas tank and replaced with fresh gas. the oil is at correct level. One time when cutting the grass the mower did rev to normal speed but only for a very short time. I'm out of ideas. Can you help? Thanks. John, I would also like to buy a repair manual for this model. Any suggestions? Thanks again.....vince.

Answer
 Hello Vince:

 Did you Replace the Gasket? The problem you described is usually the Carb needing Cleaned and Overhauled. Did you Blow the Carb Ports and Passages out with High Pressure Air? The Only other Cause is a Leaking head Gasket. Hope this Helps.

 Good Luck

 Respectfully

 John