Kohler Command Won't Turn Over

I am working on a Scotts riding mower with a Kohler Command motor. The model of the motor is CV16S. When you go to start it, it just makes a loud click and the flywheel twitches slightly. It does the exact same thing with the spark plug removed, so it is not hydralocked. Also, I was going to adjust the valves, but I found out they are not adjustable. I took the OHV cover off just to make sure, and there is no adjustment whatsoever. I cannot spin the flywheel with my hand clockwise at all either with or without the spark plug. What could the problem be? I am fixing this for someone else, but the engine did run this summer. Thanks

Check to see if the battery voltage is over 12.6 V just sitting there. Then with the volt meter attached, try to start the engine and watch the voltage. If it drops below 10.5V you have a low charged battery, or one with a bad cell and will need to be replaced.

Ok, I got it fixed. It turns out the drive belt was jammed, so it would not allow the crankshaft to spin. Thanks for hthe reply.