Kohler 26hp twin surging at high throttle, okay at medium to 70% throttle

jpilk99 · 2025-08-24T15:37:14-0400

I have a new OEM carb on here and all linkages are setup correctly. Assuming I may have a governor issue but figured I'd ask to see if anyone has thoughts on why this engine (only 350 hours) wants to surge at high throttle?

Thank you,

Jay

jpilk99 · 2025-08-24T15:44:44-0400

pmsmechanic · 2025-08-24T15:46:50-0400

Does it smooth out if you apply a little choke? Does it run smooth while mowing the lawn?

jpilk99 · 2025-08-24T15:54:26-0400

pmsmechanic said:
Does it smooth out if you apply a little choke? Does it run smooth while mowing the lawn?

Yes, it does smooth out with a little choke. Haven't put deck on to mow lawn yet....

pmsmechanic · 2025-08-24T16:04:12-0400

To me it sounds like it's running a bit lean. It's not getting enough gas. I would try mowing with it. As the governor opens up the throttle under load the carburetor pulls fuel from a different circuit in the carb. It might make enough of a difference in your case.

There is also a possibility of something blocking off the main jet just enough to cause surging. That would require removing the main jet and cleaning it out. On some engines you can do that without removing the carb. I'm not familiar with your unit.

RayIN · 2025-08-24T20:12:42-0400

pmsmechanic said:
To me it sounds like it's running a bit lean. It's not getting enough gas. I would try mowing with it. As the governor opens up the throttle under load the carburetor pulls fuel from a different circuit in the carb. It might make enough of a difference in your case.

There is also a possibility of something blocking off the main jet just enough to cause surging. That would require removing the main jet and cleaning it out. On some engines you can do that without removing the carb. I'm not familiar with your unit.

I agree. An unloaded engine might run great at WOT, put it under load and it might run hot, surge, or require frequent plug replacement. I adjust my small engines to run slightly rich unloaded. Then again, it could be fuel quality.
The first thing I try when a small engine begins running less than satisfactory is to pour ½ can of SeaFoam into the fuel tank and keep track of how it runs afterward.