Small Engines (Lawn Mowers, etc.): Kohler lawn mower surging, kohler command, riding mower

Question
In your last response, you advised to:
1) check and clean the valve breather
  A - I do not find a valve breather on this engine.  Are you sure it has one?  Where is it?

2) asked if the engine was mechanical or vaccumm fuel pump
  A - The fuel is fed through a single gravity line directly into the carb and bowl.  It is free of obstructions.  No mechanical pump or vaccumm line.

3) Have I replaced the spark plug?
  A - Yes, I replaced the plug.  No difference in surging.



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Followup To
Question -
I have a 2001/2 Scott riding mower with a 16 hp Kohler "Command" engine. It ran fine the first year but is now surging continually when running.  From prior posts, I noted that the carb could be the problem; so I disassembled it and cleaned it. It appeared very clean. No help.
In summary the engine:
- starts fine on chock.
- when taken off chock, the engine speed rises and falls coninually on about 5 second cycles.
- when I engage the blade too fast, the engine almost dies; if I hit a heavy spot in the lawn, the engine almost dies.
- If I am running for a longer period under heavy load, the surging lessens or stops.
- if I hold the governor manually be hand, the engine runs fine (no surging) but I cannot do that while mowing of course.
- the surging occurs at all speeds but is worse at higher speeds.
- I note that the governor lever is very loose and moves very freely -- should that not be damped?

I don't have a trailer to transport this pig to a repair shop, so any help that you can give will be greatly appreciated.

Thanks!

Answer -
Some governors are dampened but most are not.  More than likely the problem is in the carburetor.  Did you used an air compressor to blow out all the carburetor orfices?

Check the carburetor and intake gaskets.  If either of these leak it will surge.

Let me know about the carb cleaning.
Eric

Answer
The valve breather is normally in the valve cover.  It is a simple flapper typ disc designed to let out crankcase pressure but prevent air from entering the crankcase.

99% of surging problems are caused by the carb, not the governor, according to all the factory repair schools and books I have read.

When they say carburtor they include the entire fuel intake system.  If an intake manifold gasket is leaking then air will enter the fuel system and cause incorrect fuel delivery.

We don't see a lot of Kohlers in the shop so I need some more info.  Is there any adjustments on the carb?  Have you checked the entire fuel system from the air filter to the engine intake valve?  If any gaskets are leaking, screws loose or intake manifold warped then the engine an surge.  If everything is alright then I would clean the carb with compressed air, about 40 psi from a filter air compressor, blowing out all the orfice.

If it still surges you should check the engine RMP and adjust the governor spring tension if necessary or replace the spring (it may be weak).  We rarely find weak governor springs.  Most of the sruging problems are solved by cleaning the carb and adjusting the governor spring tension.

Let me know what you find about the fuel system.
Eric