Small Engines (Lawn Mowers, etc.): 4.0 horse/hp B&S lawnmower - dip & surge and then engine sputters to stop, horse hp, walk behind mower

Question
Hi,
I have a MTD with a B&S 4.0 horse walk behind mower.  

I've changed the airfilter, shortened the carb spring, but still the engine has this surging rev to it where it eventually dies.  It has become impossible to use.  Not sure how the engine even excellerates to run speed.

There was a loose wire from the magneto to the cut off circuit so I crimped that.  

Any thoughts?

I was going to clean out the bowl next.

Thad

Answer
Most likely the problem is in the carburetor...I would clean the bowl.

As for the spring, I would recommend replacing it with a brand new one.  The springs are calibrated to control the engine speed, accelleration.  Any Briggs dealer can get you the spring, you just need to give the dealer  your eninge model, type and code number.

Let me know if you have any other questions.
Eric