Small Engines (Lawn Mowers, etc.): engine surging, briggs straton engine, self propelled mower

Question
I have a 6.75 H.P. Briggs & Straton engine on a Cub Cadet self propelled mower That is one season old. I bent the crank this summer and replaced same with all associated items -- keys, seals, etc. Now, I have a serious surging of rpm that I didn,t have before. The Frame was turned on it's side before engine oil was drained allowing oil to escape thru carb and out thru air filter. The carb was flushed with gas and the filter was replaced.

     Model        Type        Code
     122602      0203 E1     020402 FA
Phil

Answer
Most surging problems are caused by the carburetor. Newer engines are very sensitive to any debris in the fuel system.  There may still be some oil in the carburetor.  Try cleaning the carburetor with compressed air; I set the air compressor to about 35 psi to clean carburtors.

Did you just install a new crank without taking out the cam and not touching the governor system?
Do you have a repair manual?

Let me know.
Eric