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

[jpilk99]

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]

 

[pmsmechanic]

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

 

[jpilk99]

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]

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]

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.

 

[jpilk99]

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.

Hi RayIN, just to make sure ( I use Seafoam alot - and I think it's 2oz/5 gallons of gas): You really mean a 1/2 a can? I guess the idea here is, where Seafoam is so much more flammable/combustible that it will eliminate the possibility of "bad gas" being the culprit to the surging?

 

[tomplum]

Are sure that it isn't jealous of the Deere you've got it sitting next to? Did your new carb come with a pin(s) in a bag w/ instructions perchance?

 

[jpilk99]

Are sure that it isn't jealous of the Deere you've got it sitting next to? Did your new carb come with a pin(s) in a bag w/ instructions perchance?

It may indeed have some jealously - that JD is a beast. IMHO they cut grass better than other other 'homeowner' grade mower(s). Carb did not come with a pin or instructions. What kind of pin, to do what? I have a bunch of carb cleaner "brushes", wire/needles/etc.... Is that what you meant, for the main jet clean? The carb is new so hard to imagine it's already dirty (new fuel filter). I believe I'm going to drain the gas tank and start fresh with new fuel to eliminate that possibility

 

[Alan W.]

Have you checked that your coils are working good. Those motors went through three different coil designs before finally going back to a standard coil. They can and will cause problems.
I have had to replace mine and I think another one is acting up now. Surging and it aint the carb.
Use an infrared temp gun to check the exhaust pipe temps. Bad coil will be cooler.