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Curtis B.
Curtis B., Technician
Category: Small Engine
Satisfied Customers: 28653
Experience:  have worked on and around most engine models for 35 yrs./Polaris ATV expert
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I have a Kohler 26 HP twin cylinder engine (Courage Pro V-Twin)

Customer Question

I have a Kohler 26 HP twin cylinder engine (Courage Pro V-Twin) on a Sears lawn tractor purchased about three years ago. Ran fine until I serviced the engine a few weeks ago. I changed the oil (which I have done before) changed the fuel filter (which I have done before) and changed the plugs (first time) with Champions of the same specification as came with the engine from Sears. Now the the engine runs fine when it is first cranked up and is cold but after it warms up well (about ten to 20 minutes) it begins to lose power and runs somewhat rough. Thought at first it was starving for fuel, so I changed the fuel filter again though it seemed to be getting adequate fuel via inspection of the clear fuel filter body. Again, runs fine when cold but after so many minutes starts to run or skip, loses power, etc (i.e., basically runs the same). Removed the newly-replaced plugs and the driver's right side plug showed what I think are clear signs of misfire (heavily sooted\blackened) compared to the still new looking left plug. Replaced the new plugs with the old plugs in case new plugs were defective while the engine was warm. Immediately cranked up and ran well with plenty of power for about thirty minutes and then agian began again to skip or run rough. At this point stopped the engine, got off and placed my hand on each of the valve covers and noticed the driver's right side valve cover (the one that blackened the new plug) was significantly hotter than the other (the cooler side seemed only luke warm in comparison) I wonder if the left cyclinder is starving for oil due to some issue with the new filter or some other reason; I am going to change the filter again, after that I am not sure where to go from there. One note, taking the mower up mild hills and run with blade on versus off (i.e., incereasing load) seems to bring on the misfiring\overheating quicker. Any insight would be appreciated.........
Submitted: 6 years ago.
Category: Small Engine
Expert:  Curtis B. replied 6 years ago.

curtis b :

Welcome to JUST ANSWER small engines, let me try to help you !! After studying your question and looking at the results you have achieved, I think you could have a valve problem. Can you get the numbers off the engine? Kohler uses many setups, and I would like to be sure before telling you a lot of non sense.

JACUSTOMER-8om8nssy- :

Apologies for delay in response; changed the oil filter and did not refill lost oil. Problem appears to be solved as both valve covers seem much more even in temperature (checked couple times while running and when stopped) with power and smooth running generally restored.....was able to finish mowing a large enough area that before it would have likely overheated and started skipping before finishing....I would offer that the first oil filter was defective an for some reason not passing enough oil or as much as I hate to admit....the engine may have been slightly overfilled with oil and submerging the spray holes......could explaing issue of noticing the problem moreso when going up hill or under load......I did however check the oil level when changing and before cranking up and seemed ok.....I run synthetic oil in the engine and when fresh\clean it can sometimes be hard to confirm the exact oil level......will have a better idea of all this tomorrow when I run the mower some more tomorrow......

curtis b :

Ok, you might want want to look into whether this model needs the valves adjusted on a regular basis.