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I have a CC lawn tractor with a 22 hp Koehler twin engine and it’s about 3 yrs old. Two seasons ago the engine was surging and eventually it stopped so I was thinking it was a fuel issue. Now today, for the first time this season, I’m noticing that it’s surging again and I only notice it at half throttle! I only use non ethanol gas and I always add stabilizer.

should I be concerned with this surging or just wait it out to see if it’s a fuel issue? Thanks

surging is too much air, or not enough fuel... most of the time a blockage in the idle circuit of the carburetor. it can also be a leaking intake gasket allowing in air past the carburetor.
post the model and spec numbers.

Scrubcadet10 said:

surging is too much air, or not enough fuel... most of the time a blockage in the idle circuit of the carburetor. it can also be a leaking intake gasket allowing in air past the carburetor.
post the model and spec numbers.
View attachment 56529

https://www.jackssmallengines.com/jacks-parts-lookup/kohler-model-locator.aspx

Click to expand...

Here it is, thanks!

Rickcin said:

Here it is, thanks!

Click to expand...

Scrubcadet10 said:

surging is too much air, or not enough fuel... most of the time a blockage in the idle circuit of the carburetor. it can also be a leaking intake gasket allowing in air past the carburetor.
post the model and spec numbers.
View attachment 56529

https://www.jackssmallengines.com/jacks-parts-lookup/kohler-model-locator.aspx

Click to expand...

Will running the mower until the end of the season (November) be harmful since I could then get it back to the shop to be serviced?

I wouldn't think so... I've personally never seen major issues/damage caused by surging.

Scrubcadet10 said:

I wouldn't think so... I've personally never seen major issues/damage caused by surging.

Click to expand...

Thanks! So I will continue to use it and send it in for service this winter.
It’s just odd since it was doing this over a year ago and then it ran fine until now?

Sometimes a shot of this https://www.walmart.com/ip/Sea-Foam...lsxcGiBfTJmioHGVOaxoCOcYQAvD_BwE&gclsrc=aw.ds will cure things.

bullet bob said:

Sometimes a shot of this https://www.walmart.com/ip/Sea-Foam...lsxcGiBfTJmioHGVOaxoCOcYQAvD_BwE&gclsrc=aw.ds will cure things.

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I do have a can of that and have used it in the past.

Its unexplainable since this raging has happened in the past and then stopped for a season and a month and just started happening again?

Rickcin said:

I only use non ethanol gas and I always add stabilizer.

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The stabilizer's job is to keep the ethanol in solution with the gasoline. If you don't have it, then the ethanol separates and you'll get portions of fuel with higher than 15% ethanol to gasoline ratio, which a normal engine can't possibly burn.

But, since your fuel has NO ethanol to begin with, I'm wondering why you bother. Stabilizer does nothing for non-ethanol fuel.

Born2Mow said:

The stabilizer's job is to keep the ethanol in solution with the gasoline. If you don't have it, then the ethanol separates and you'll get portions of fuel with higher than 15% ethanol to gasoline ratio, which a normal engine can't possibly burn.

But, since your fuel has NO ethanol to begin with, I'm wondering why you bother. Stabilizer does nothing for non-ethanol fuel.

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Stabilizers also contain anti-oxidants which prevents the fuel from oxidizing during prolonged storage and subsequent varnish formation and sediment. A little 2-cycle oil will do the same thing.

mehan said:

Stabilizers also contain anti-oxidants which prevents the fuel from oxidizing during prolonged storage and subsequent varnish formation and sediment. A little 2-cycle oil will do the same thing.

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So perhaps adding stabilizer to non ethanol fuel is actually causing the engine to surge?

With that motor meeting Ca emissions the ports and jet system has the smallest possible holes to allow it to run. A piece of corrosion smaller than 1/10th a grain of salt in it or a layer of film will cause surging. Just fixed one yesterday. Although the carb can be modified to correct the problem its illegal and guarantees a revisit to the shop sometime in the future. This info is up front to the owner as Im not out to turn it into a scam.

CaptFerd said:

With that motor meeting Ca emissions the ports and jet system has the smallest possible holes to allow it to run. A piece of corrosion smaller than 1/10th a grain of salt in it or a layer of film will cause surging. Just fixed one yesterday. Although the carb can be modified to correct the problem its illegal and guarantees a revisit to the shop sometime in the future. This info is up front to the owner as Im not out to turn it into a scam.

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Well we can thank CA for all of their crazy regulations that often cause more harm than good️