Kohler Command CH960

[BLES]

36hp Command horizontal
(I don't have the spec numbers with me now.)

Starts and runs at all rpms, as nice as any one of these engines I've ever seen. Flushed fuel tank and lines, cleaned carb (even though it was spotless).
Everything appears good and it runs SO nice.....

.... until under load and then it just slows for about a minute until barely at an idle. Stalls if continued. Choke doesn't help, makes worse. If load is removed it gains back to full rpm.

Possible ignition advance problem??

Looking for ideas.

BLES

[bgsengine]

power balance test, see if it's running on one cylinder.

[38racing]

Could it be governor issue?

[KE4AVB]

As BGS suggests it sounds as if it is running on one cylinder. Note v-twins are known to run very well on one cylinder until loaded. I had customer to question my repairs because of this swearing it a fuel issue and not a cylinder problem. But note this engine is most likely using a twin barrel carburetor so it can be a partial clog on one side of the carburetor that only affects the operation when under load.

Can even be a cylinder dropping out under load too. I had a Generac engine last year that was dropping a cylinder under load where the plug wire terminal was rusted. Installed a new terminal and all has been well except for an unrelated voltage regulator failure.

[BLES]

Thanks guys. I'm not near the engine now, but appreciate the ideas. I THINK I already checked for both cylinders firing but not sure. Also, governor.... I've seen a couple of these where they were sticky. Again, this one acted different, but....
I learn something new about something every day!

[KE4AVB]

Sooo your still alive. The day you stop learning is the day you start on that trip to the great beyond. Let us know what you find wrong we all learn from each other.

[BLES]

Update:
Had a chance to look at it again. It is running on both cylinders and governor appears to be working although I didn't have opportunity to load it as it would be in use. However, I think I've found the problem. They have done some work on this machine and there is a huge "drag" on the machine. I think the engine is 100% and there is a problem with the machine, requiring more power than this engine produces!
BLES

[Skywatcher]

Hi BLES

A very quick and simple way to see if a V-twin is firing on both cylinders is this:

With the engine cold, have a friend wrap one hand around each exhaust pipe and start the engine. If he or she takes both hands off at the same time, the engine is firing on both cylinders. If only one hand comes off, the remaining hand is the dead cylinder. You can't get much simpler than that. All the best,

Sky

[BLES]

Yes. I usually just grab an infrared thermometer. Guess that's easier for me than finding a friend!

[KE4AVB]

Yes guinea pigs are hard to find at times. I did by me one of those infrared temp guns myself, much cheaper than the doctor visits and bandages.