Kohler CV740 running rough under load.

[Auto Doc's]

We need the full model and serial number to reference the correct parts catalogues.

This is what typically happens when a coil stops working under stress (load). The engine does not rock or shake, a coil just quits.

A quick test:

Run at high RPM, use a spray bottle and hit each exhaust head pipe with a quick stream of water. The cylinder that is working will burn off the water instantly. The one not working correctly will have a delay burning off the water.

Swap plugs to be sure it is not a plug that is failing and retest with the water. See if the issue switches sides.

Perform a compression test with the throttle in the wide-open position and compare the readings from side to side, they should be pretty close.

This may lead to having to pull the fuel tanks off and flush them out and do a thorough inspection. I've pulled some strange stuff out of fuel tanks like candy wrapper and small plastic bags. Old grass clippings and dirt are pretty common. Just looking down the fill opening is not an "inspection".

 

[rwhelipilot]

Carb float level could be set low. Restriction in fuel delivery to carb.

After sitting for a year, I decided to work on this some more. I have really dumped a lot of money and my own labor into this mower and after trying everything else, I remembered what my local repair shop told me last year. They said that these cheap Chinese carburetors that I had installed are hit & miss. Some will work and some won't. I decided to rebuild the original OEM carburetor. I reinstalled it today and the mower now has plenty power and no spitting & sputtering under load. That Chinese carburetor was supposed to work on 25 & 27 HP. It may have been OK on 25 HP, but evidently it was starving the 27 HP when under load.

 

[slomo]

They said that these cheap Chinese carburetors that I had installed are hit & miss. Some will work and some won't.

What I've found is don't buy the cheapest listed priced carb you can find off fleabay or scamazon. Say the lowest listed price is $19.95. Get one that cost $29.95 for example. Since I've started doing this, my good carbs have been way higher in luck for sure.

They are a crap shoot. I typically open then up and make sure they look legit. Some I've had to mod a bit to make them work. I pressure test the needle/seat at 7psi for 30mins. Make sure the float is level or slightly higher than level.

I decided to rebuild the original OEM carburetor. I reinstalled it today and the mower now has plenty power and no spitting & sputtering under load.

This is typically your first and best move. Might take 3 or 5 cleanings to get the OEM carb to run right. I use a cheap 120 volt hot plate, garage sale pot, water and Pine Sol. Remove all plastic and rubber parts. Gently boil the carb for an hour. Blow out with compressed air. Get a hot plate and pot off facetrash market place.

 

[sgkent]

After sitting for a year, I decided to work on this some more. I have really dumped a lot of money and my own labor into this mower and after trying everything else, I remembered what my local repair shop told me last year. They said that these cheap Chinese carburetors that I had installed are hit & miss. Some will work and some won't. I decided to rebuild the original OEM carburetor. I reinstalled it today and the mower now has plenty power and no spitting & sputtering under load. That Chinese carburetor was supposed to work on 25 & 27 HP. It may have been OK on 25 HP, but evidently it was starving the 27 HP when under load.

Congrats and thanks for sharing the solution.