Question about Kohler CH25 PA-CH730-0040 Command Gasoline Engine

I have a Kohler Command Pro (CV740S) engine, 2nd one on a Super Z with only 171 hours on it. I have replaced the cam, lifters, oil, plugs, have had the valve worked on and head cleaned. Still will not crank. I will replace the flywheel key tomorrow just in case the old one got damage. Your held is appeciated. Thanks, David Lancaster

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The engine is NOT burning clean and the exhaust gases contain unburned fuel which burns in the muffler. This could be a mixture problem or possibly a timing problem or maybe the exhaust valve timing is wrong or a burned valve or seating problem. Do a COMPRESSION test as a first step.


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Even though the engine is 13 years old but has low hours it could just be that the rings are gummed up and sticking in the groves and not doing their job properly. Before you consider pulling the engine apart for a ring replacement and bore hone, you could try this procedure.
Remove spark plugs and pour some engine flushing product like Wynns or Nulon into each cylinder. Turn engine over by hand to distribute the flush around the pistons and allow to sit for a day or so turning the crank occasionally and adding small amounts as the flush drains past the rings. The flush should soften any build-up of gum around rings and the bore. Before replacing plugs use a torch to see that there is not excessive flush sitting on top of pistons. If so wind over with starter to blow out excess. Replace plugs and put any remaing flush in sump and then fast idle engine until hot and then drain and replace oil and filter (if one fitted).
However if rings are badly worn there may not be much improvement and it is possible the oil use will increase. The cylinder with the badly fouled plug may also have a broken ring/s. Oill changes should be done every year or after 50 hours running, whichever comes first.
Let me know how you get on by posting a comment. Myki R

Testimonial: "I considered the possibility of stuck rings and this adviser offered a practical way to rule that out. Thanks!"

Source: I have a 1997 Kohler Command CH25S in my small

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first torque to 16ft/lbs in a x patt. then 30ft/lbs in a x patt. for head the intake gaskets connecting to the head should be 12 to 17

Source: We are replacing head gaskets

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