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

[jpilk99]

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.

Hadnt really considered coil(s) as they're "firing". But I've never seen any this complicated so I'll look into. I can't stand Kohler products for this reason: They have to do almost everything different than all other types. Kindof infuriating

 

[ning]

Mine surges but still runs and I'm too lazy & scared to do much about it. I'm always afraid of getting those linkages taken apart and put back together right...

 

[stevem5215]

For surges it's probably a dirty carb. Go to Lowes or Home Depot and buy the "Mechanic in a Bottle" product. Dump it in and surge goes away. Did that on my 24hp Briggs a few years ago. Still working well.

 

[tomplum]

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

I dunno what is going on w/ Kohler since somebody scrambled the letters on their stationary. (Rehlko) It seems like they've changed vendors on somethings. Or made one part number to fit multiples. Good idea I guess. Example: Certain carbs now come with a set of pins that I think are throttle arm stops that you install in the field. I had either a 7000 or Courage that did is why I brought it up. Try the donor can approach. Take a few feet of 1/4" fuel line, hook it to the fuel filter and drop it in a gallon gas can. Easy way to check your fuel supply.

 

[RayIN]

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?

Ya, I mix ½ can to 5G gasoline if I suspect the carb, tank and gas lines are dirty or contain water. Todays gas can go bad in 30 days without stabilizer.

 

[jpilk99]

Update: I FINALLY got the mower deck on (needed to buy the attaching hardware) and once I fired up the PTO, the surging went away. But when I stop mowing, within 15 seconds, the surging comes back. Is it still a main jet issue you think???

 

[RandyT]

No, it is an idle circuit issue. When not under load an engine runs on the idle circuit of the carb. Even at full throttle the idle circuit is the primary, and the high speed jet doesn't come into play unless under load.

 

[jpilk99]

No, it is an idle circuit issue. When not under load an engine runs on the idle circuit of the carb. Even at full throttle the idle circuit is the primary, and the high speed jet doesn't come into play unless under load.

Thanks Randy

 

[jpilk99]

No, it is an idle circuit issue. When not under load an engine runs on the idle circuit of the carb. Even at full throttle the idle circuit is the primary, and the high speed jet doesn't come into play unless under load.

Randy/all,

I'm trying to find a diagram that shows the "low idle" circuit and striking out. I believe this is the carb part number: 32 853 25-S . Can anyone highlight where, inside the carb, is the low idle circuit - so I can check and clean it? Oddly, I put a new carb on it... but yes, it was a $35 dollar one on amazon. Thinking this may be my issue right here...... But still, I'd like to know in case the old/original carb needs attention. Thank you.

 

[tomplum]

This may be helpful for you. I see they have the Command carb at the bottom which shows a model w/ an accelerator pump but hopefully similar enough to get the idea how it works. Typically a surge that goes away under load is considered a low speed circuit issue as Randy has pointed out. Consider too that intake gaskets and seals can play a part as well. https://outdoorpowerinfo.com/repairs/#id_kohler