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Small Engines (Lawn Mowers, etc.)/Kohler model CV724-69551 Backfires


QUESTION: This engine is in Craftsman tractor.  Starting the tractor now when it is really cold is hard on the engine.  In order to start I set the throttle half way through and open the choke.  When the engine starts I "play" with the choke to keep it running and after a minute or so I open the throttle to increase the RPM.  When I do this the engine starts to backfire, about once every 5-10 seconds.

I changed the spark plugs, air filer, fuel filter and filled the tank with fresh gas.  I think it helped a bit as the backfires are a bit less frequent and not as loud.  However they are still there.

What would you suggest to check/do next?

It seems like cleaning the carburetor is another thing to do but since I have never done this before I am not sure if I should try to do it myself.

Thank you.

ANSWER: As you mentioned I would start with cleaning the carburetor.  You can download the service manual from Kohler's website.

Copy/paste the URL below and you will see a link to the service manual:

Do you have an air compressor and a digital camera?

DO NOT adjust anything until you review the manaul!  Carb removal is pretty straight forward and no need to mess with any GOVERNOR parts...the control links can be dis-connected by manuevering the carburetor once it is loose.

Let me know about the air compressor and camera.


---------- FOLLOW-UP ----------

QUESTION: Thank you for your reply and the pointer to the service manual.  I have a digital camera but I do not have an air compressor.

Also, a local small engine mechanic whom I called recommended using high octane gasoline and adding Star-Tron fuel treatment to it.  I guess this would be, perhaps not so good but still, one way to clean the carburetor and more.

ANSWER: It probably will not hurt to use the better fuel and fuel may help it run better.

To really clean the carb you need an air compressor, even a small one, $40 at Harbor Freight if you catch a small one on sale.  Of course you have to buy a hose and the blow gun accessory so you can easily get to $60 pretty quick.

You could always remove the carb and take it to a local shop for cleaning/rebuilding but there is no guarantee it will fix the problem as you might have a fuel pump issue or something in the fuel tank, moisture, fine dirt or something else.

I doubt the fuel pump is the issue but you never know until you test it.  You need a vaccum pump/gauge to really check the fuel pump.

Try the fuel and additive and see if it helps.

---------- FOLLOW-UP ----------

QUESTION: Hello Eric,

Thank you again for your reply. I will try the additive first and if this does not work I will try to clean the carburetor one way or another.

Thank you,

FYI, I use fuel stabilizer year round in all my power equipment.  It works well but it's not a cure all.  Carbs today are designed for low emissions and this leads to very sensitive carbs.  Last time I used my Snapper it was not running well so after about 2 years of using it I'll have to take the carb off this spring and give it a good cleaning.

Let me know how the additive works.

Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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