Puffing back through carb, Kohler CV730S

[Gravelier]

I have a Kohler command pro CV730S. It is burping back the carb (puffs of gas vapor coming out the carb) at idle. Seems like a valve problem but it is supposed to be hydraulic valve lifters. No adjustment. loses power under load in heavy grass and uphill. But not every time. I did a governor adjust. Didn’t make any difference.

15 year old engine with 300 hours. I pulled the plugs. The left was black and the right was white. I put in new plugs and mowed grass. Two hours. Both plugs were clean, white. I don’t have a good compression tester but both sides were exactly the same On a cold engine. New fuel pump, new filter, good fuel flow from tank by gravity into a cup.
About 20 hours on oil and filter change, 10w-30 oil conventional.

thanks for your help

 

[VegetiveSteam]

I have a Kohler command pro CV730S. It is burping back the carb (puffs of gas vapor coming out the carb) at idle. Seems like a valve problem but it is supposed to be hydraulic valve lifters. No adjustment. loses power under load in heavy grass and uphill. But not every time. I did a governor adjust. Didn’t make any difference.

15 year old engine with 300 hours. I pulled the plugs. The left was black and the right was white. I put in new plugs and mowed grass. Two hours. Both plugs were clean, white. I don’t have a good compression tester but both sides were exactly the same On a cold engine. New fuel pump, new filter, good fuel flow from tank by gravity into a cup.
About 20 hours on oil and filter change, 10w-30 oil conventional.

thanks for your help

What were your compression readings?

 

[Gravelier]

What were your compression readings?

I’m embarrassed to say that my compression tester is a HFT. That said and taken into consideration, both cylinders were 68 psi.

 

[ILENGINE]

Not sure I would trust those readings. But anyway the mininum on the Command twin should be 160 psi. I am thinking that you are running on one cylinder most of the time. Could be valve issue, but could also be ignition issue.

 

[Its Me]

set the valve lash, that is why it is coughing.

 

[Gravelier]

set the valve lash, that is why it is coughing.

Thanks everyone

next question: Where can I find information on how to set the “valve lash”. Should it be set on a warm or cold engine.

 

[Tiger Small Engine]

Thanks everyone

next question: Where can I find information on how to set the “valve lash”. Should it be set on a warm or cold engine.

Kohler Command has hydraulic lifters so no setting the valve clearance. Remove carburetor and thoroughly clean and replace and see how it runs. White plugs indicate you are running lean on fuel.

 

[Gravelier]

Up date. As I have dug deep into the Kohler tech manual on my engine I believe I have isolated the problem. Previous owner had installed an aftermarket carb on the engine and it’s not the right carb. I need to find the right carb. The search has begun.