Kohler Courage surging issues

[Tubefreakz]

What is the color of the spark plug? If it is white, that is caused from a lean fuel mixture. Lean is caused either from air leaks or most likey gummed up jets. You can also test to see if it runs better with the choke on. This is also an indication the mixture is too lean.
Remove the carb, float bowl, and the brass jets screwed into the carb below the float bowl. Spray the jets and passages with carb cleaner. I also poke a wire through the holes in the jets with a wire I pull from a wire brush. This wire is flexible enough not to damage or enlargen the holes.

I am not sure how common this is but the carb in my pressure washer has a steel plug and a rubber seat (image below). The rubber swelled, thus lowering the float to the point the fuel level in the bowl was below the jets. This was the cause of the lean condition in my case. I purchased replacements on ebay and problem solved. I could have also just replaced the carb but I was confident with my diagnosis.

 

[hamiltzp]

If it smooths out under load then I'd wager that the pilot circuit is too lean. It may take an adjustment of a needle or removal of the pilot jet and a little massaging with a pin drill. Usually if it's just a lean pilot, then .002"-.003" will cure it. To get it right you'll have to figure out the diameter of the jet, then calc the area and add about 10 to 15 percent to clean up that circuit.

This of course is after you verify no leaking gaskets or seals.

You are referring to the carb, right? I had someone on another site ask about the fuel pump, but I don't have one. My mower is gravity fed.

 

[The_Eric]

You are referring to the carb, right? I had someone on another site ask about the fuel pump, but I don't have one. My mower is gravity fed.

Yes, the pilot circuit in the carburetor. If you can post a couple of pics of the carb we can tell you if it has an adjustment needle or a fixed pilot jet.

 

[hamiltzp]

What is the color of the spark plug? If it is white, that is caused from a lean fuel mixture. Lean is caused either from air leaks or most likey gummed up jets. You can also test to see if it runs better with the choke on. This is also an indication the mixture is too lean.
Remove the carb, float bowl, and the brass jets screwed into the carb below the float bowl. Spray the jets and passages with carb cleaner. I also poke a wire through the holes in the jets with a wire I pull from a wire brush. This wire is flexible enough not to damage or enlargen the holes.

I am not sure how common this is but the carb in my pressure washer has a steel plug and a rubber seat (image below). The rubber swelled, thus lowering the float to the point the fuel level in the bowl was below the jets. This was the cause of the lean condition in my case. I purchased replacements on ebay and problem solved. I could have also just replaced the carb but I was confident with my diagnosis.

View attachment 326919

The spark plug is brand new. It has less than 10 minutes of run time at this point. Looking at the old one, it doesn't look white or black, just kinda rusty.

It runs OK with the throttle all the way open, other than the surging and roughness. If I try to apply the choke or if I reduce the throttle, it wants to stall.

 

[The_Eric]

What about with the blades engaged? Smooth and even?

 

[The_Jeff]

Surging without load is lean like ten people already mentioned. Running the blades adds a load and should smooth it out. Carbs are calibrated lean for emissions but they're counting on "real gas" and E10 makes things leaner still.

I got a "numbered drill bit" kit on ebay/amazon for under ten bucks and figured out my main jet size, then overbored it by two drill bit sizes. Stopped the surging.

 

[ripcord]

Have you ever changed the fuel filter? Restricted fuel flow can cause lean surge. Be sure not to use an automotive fuel filter as they can be too restrive for a gravity feed system.

 

[cudavid]

Surprised not to see this idea: surging usually is a lean condition, yes dirty carb, but possible solvent to opening* mixture screw. Assume this is a float carb. Main jet bottom , may have spr8ng loaded screw, this is high speed. Is surging slow speed open side mounted smaller screw, try 1/8 turn, same with surge high speed, try 1/8 turn.
Also drop bowl and look for water.

 

[hamiltzp]

Mostly good now. So here's what I finally did. I found TDC on the compression stroke, and then moved the flywheel about 1/8 turn past that. I adjusted the valve lash on the intake for .005" and on the exhaust for .007". Those are the values in the service manual that I downloaded from Rehlko's web site, so that's what I wanted to start with. I know some people use slightly larger values. The result is that the engine starts noticably easier and quicker. It no longer pauses for several seconds after one crank. Although it surged for about 10 seconds, it mostly smoothed out after that. I could still hear it surging very slightly, but generally it ran pretty smooth and didn't have the pronounced surges it had before. It still shuts off a little rough, so I might have to look into that. I was told that the anti-backfire solenoid might be sluggish. Not sure if spraying some carb cleaner in the carb, or putting some Marvel Mystery Oil in the gas would fix that or not.