Small Engines (Lawn Mowers, etc.)/Kohler CV25S on Mower


QUESTION: Hi Erick, I have a MTD zero torn mower with a Kohler 25 Command motor. My problem started when I was mowing, every time i made a quick spin the mower would lose rpm but catch right back up. When I was finished I idled the mower down and it died. Could not restart so I drug it back to the garage. Next morning I noticed gas on the floor. Also air cleaner has oil residue in it. Tried to start and it bellowed blue smoke severely and spit oil out of the muffler. Ran for 10 to 15 seconds and died. Filled the garage up with smoke. Since then I have removed and cleaned the carb. Soaked it overnight in a parts cleaner. Blew it out with air and installed a carb. repair kit from Kohler. Well nothing changed. Still blowing smoke with oil. I did a compression check. I get 180 and 175 on the two cylinders. I did notice one cylinder lost compression if I kept cranking on the motor. New fuel filter and new air filter has been added. Any suggestions would be helpful. Thank You.

ANSWER: Did  you check the valve clearances?  Does the oil smell like gasoline.

The most common cause for smoking that bad usually starts with the carb, a leaking inlet needle, seat or bad float.  Too much gas can enter the engine oil thinning it which allows the oil/gas mix to get past the rings and valves leading to the blue/white smoke.

Some carb inlet needle seats need to be installed with one side up.  Was the inlet needle seat replacable on your carb?


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

QUESTION: There was no inlet needle seat in the kit so no it was not. Replaced needle and float and also the gaskets. Could I have thinned down the oil so much that i should change it to see if the new carb. parts could have fixed the issue? I have not pulled the valve covers off. I will check the oil for a gas smell tomorrow.

Yes, I would change the oil.  If you have filter, change the oil, remove and drain the filter.  Run the engne with the old filter until it is at operating temperature.  Change the oil again and replace the oil filter.  The goal is not to ruin a new filter if there is gas mixed in the oil.  


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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