Small Engines (Lawn Mowers, etc.): B & S Lawnmower Engine, lawnmower engine, air leak

Question
Model 92908, type 1224-01, code 7202225...
Sent for rebuilt kit and rebuilt carburetor with new diaphragm.  started up, adjusted needle valve.  It did not run smoothly when I tried to speed up the motor.  It stopped, died and I finally got it to run at high speed but it had a chase (rolling) effect.  It would not run smooth, the engine always ran smooth before and could be idled down without any problem.  When you are mowing with it , it keeps chasing and if it gets into heavy grass it dies down (stops running).  I would appreciate any help you can give me.

Answer
Those old carbs are notorious for warping, causing air leak and poor performance.  One thing you can try is to remove the carb from the tank, then remove the fuel pipes from the carb, they pull out but they can be stuck pretty good.

With the fuel pipes removed, use a flat file and run it across the bottom of the carburetor.  The file will remove material from high spots; these areas will be shiny.  The low spots will be dull.  Fill the carb base until most of the surface is shiny but don't take off too much material.

Reassemble and see if it runs better.
Eric