Small Engines (Lawn Mowers, etc.): snappper pro 48, surging

Question
i have a snapper pro 48 commercial wide path walk behind mower model# splh140kh. the engine is a kohler command 14hp pro series model# cv14t. it lopes, revving up and down, at idle and mid-range but not full throttle. cleaned the carb and jets, replaced the fuel, filter and lines as well as the butterfly shaft. also tried adjusting tension on governor spring. what do you think??? suggestions???

Answer
I think you'll need to go back through the carburetor.  You're describing surging, which often fades away at full throttle or under a load.  The problem is that it's probably running a little lean and that can damage the engine.  You may also be looking at replacing the carburetor as the only way to get one really clean is with a soak can or ultra-sonic cleaning, and that's not 100% effective either.  Thanks, PK.