Small Engines (Lawn Mowers, etc.): surging FH500V Kawasaki 17 hp, air leaks, steel balls

Question
JD LX277 yr2000, surging-hunting at half throttle or more, 550hrs on engine, perfect maintenance, disassembled carb, cleaned it although it was spotless, actually got a little worse, I've been doing small engine repair for 20 + yrs, first of these engines that I've ever had, bought it new, this the first issue I have had with it, sounds like restriction in the high speed circuit, I can't believe it is though, any suggestions???

Answer
4 cycle engines will surge for a couple of reasons.  First would be lean fuel conditions and what you did would be my suggestion along with flushing the tank flushing the lines putting a new fuel filter on it is kind of things.  The next is an air leak.  Any air leak you can inspect in a few places along the fuel intake circuit.  The 1st place I would check would be the carburetor mounting to be sure it is flat and no air leaks are present between the carburetor and the manifold next inspect the fuel manifold to be sure there is no damage to the manifold, cracked, split like that and then where the fuel manifold bolts to the engine that area should be inspected and new gaskets put it.  The last way would be a governor issue.  Kawasaki uses a mechanism utilizing a plastic housing that holds steel balls I have seen these melt or crack.  The only way to check this would be to take the engine apart.  I hope that some of this information will help you out best of luck on your project.