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To test if it's a valve issue, does it turn over properly if you remove the spark plug?
To make sure I'm giving you the correct information and specifications can you please give me the model, spec, and serial number off the blower housing?
I am at work and not looking at the mower right now. However, if you've ever heard a car whose timing in is too advanced that the motor won't hardly turn and will not turn unless I choke the hell out of it. That is what I experience. I am going to burn my starter up if I haven't already. THis is what I am up against.
It's certainly most commonly the valve adjustment that causes this, but there are some other potential reasons as well, such as faulty compression release, parasitic loads on the engine, internal binding, electrical problems, etc. Taking the plugs out is a quick and easy test to determine if the valves are indeed the culprit. The reason I was asking for your model information is that some Kohlers use hydraulic lifters so the valves are not adjustable.
To get started let me post a link to what I believe will be the correct manual for your engine.
Please let me know...
Glad you got the answer you were looking for. You'll find that specific information on pages 10.12-10.13 of the manual I posted for you assuming it's a Courage SV-720 series engine. Only trying to give you correct information rather than lead you to the wrong conclusion.
Take care and thank you.