Puffing back through carb, Kohler CV730S

Gravelier

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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

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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?
 

ILENGINE

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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

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

Gravelier

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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

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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

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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.
 

Gravelier

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Well, to answer a couple questions on my Dixon Kodiac. I had complained about the engine huffing or puffing back out the carb. Someone had said I needed to adjust the valves. I had downloaded the tech manual to see if there was adjustments that could solve my problem. The manual says that this huffing is due to a carb adjustment issure. Turns outs that there was an aftermarket carb on the Kohler CV730, and not the right one. The manual goes through a procedure to adjust the carb low speed idle. Turns out the carb didn’t have a low speed idle adjustment. So, I went looking for the correct carb. I found one at a recognized Kohler dealer. It was $600. Seems like a lot when the carb is half the price of a new engine. Checking further, I referenced the carb specified by this dealer against the Kohler specified carb for my engine. Turns out that carb would work on a CV725, but not recommended for the CV730. Well, maybe an Amazon carb would work.

I ordered a carb from Amazon that appeared to be the correct configuration, It has a low speed idle adjustment screw in the right place. As it works out, there is a hole in the bracket over the carb in just the right place to put a thin blade screw driver on the low speed jet. Amazon shipped the carb to me via USPS. My great mail person decided that maybe someone else could use my carb more than me. Although I received a notification that the carb was delivered in my mail box, it wasn’t. I complained to the post office, and they tried to track it down. My neighbor received a post card asking if they had receive an item in error and if so, would they put it back in their mail box and the post office would pick it up. A week later, I went to the post office again and asked whether they had tracked it down. They denied sending out post cards, and told me that it had been correctly delivered. I went to Amazon and told them what had happened. They were good enough to send me another carb and said if it ever showed up, would I kindly send it back to them. It never did.

So, the correct carb in place, I was able to adjust it correctly and the puffing problem went away. Also, with the new carb, I was able to adjust the governor and the bogging down in heavy grass and uphill went away.

Someone had suggested that I needed to adjust the valves. Turns out the Command Pro engines have hydraulic valves. No adjustment possible.

Another problem that I had was in the electrical. It would start fine, but you could not release the brake or move the control arms without killing the engine. I did find the correct electrical diagram at Jack’s Small Engines. However, I could not find the short. There is a vertical plate between the battery and the back of the engine. The space is about 3/4". The wiring harness is at the bottom of the space and the hydraulic hoses cross above the wiring and prevent lifting it out to inspect it. I’m thinking that the problem is in one of the switches. There are 3 circuits that go through the brake switch and 2 circuits that go through each control arm switch. The brake switch is easy to get at, however, to get to the control arm switches, you have to drop the whole control arm assembly. There is no way to get to either without major disassembly.

I wired a switch in the kill wire at the engine. The switch is on, brake on, control arms out - in order to crank the engine. Switch off, and you can brake off, and use the control arms for driving. However, try to engage the PTO, and it blows the fuse. You can’t just pull the wire connector off the PTO switch as the start circuit and run circuit go through the PTO switch. I pulled power off the hot wire on the ignition switch, to a separate switch and fuse, to the PTO. The only thing not working is the hour meter. The hour meter is supposed to run when the PTO is on. It is presently bypassed. I’m going to install a separate hour meter and tach. Its been a battle. Everything works and it won’t crank without the safeties engaged. I think I’m ahead. Too soon to say I’ve won.
 
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