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I have the same issue on craftsman with Kohler CV491S - 27501 engine. A coworker gave it to me and just trying to get it running. Won’t turn with spark plug in on compression stroke but take spark plug out and it will turn with less resistance. Flywheel key looks okay so I’m thinking it’s the camshaft and acr. Can anyone confirm it? Is there anyway to know for sure that’s what it is? I don’t have much backstory on mower other than it quit running so he put it in garage and left it for 8 years. His loss is my gain if I can get it running for cheap.
I went through the whole engine, replaced gaskets, seals, plug, coil, carb and starter solenoid and it still wouldn’t crank. I finally pulled the flywheel and found the sheered key. Replaced the key with one from tractor supply for 99 cents and it’s running as good as new. I wish I would’ve checked that first but I did learn a lot so it wasn’t time wasted. Thanks for all the help guys.
I have seen a similar issue on another Kohler engine. Unfortunately, it will most likely require internal engine repairs. Do a compression test on each cylinder and compare to the specs for your engine. It most likely requires a valve adjustment for compression release during starting or the camshaft may be damaged. On my engine, the camshaft lobes were worn badly. So the valves were not opening and closing at the correct times. They were opening late and closing early essentially staying closed too long. The normally egg shaped lobes were worn down to nearly circular in shape. This you wont find until you open the crank case. I replaced the camshaft with new along with a few bent rods. If you get this far, make sure you examine all the rods, rockers, valves open and close okay and are not bent, and for play or bends in the piston rods or any other evidence of damage. Get the full assessment and order all parts/gaskets needed at once. After installation of the parts, the valves will require adjustment per the engine service manual.
