mower turns over...kinda

I'm going to say that since you have tried everything we have told you to try and ave even put another starter on it and had the same result then I'm going to say it is a batter that is weak if you can spin it by hand and it will spin fine without the plug and since its not OHV then the valves wont be out of adjustment so take the battery out and take it to a auto zone or some place that can load test it for you i see them all the time with 12.5 volts in them but still wont crank the engine good luck

I wouldn't think the valves were out of adjustment but I wasn't sure. So if it's an L valve the chances of them being out of adjustment are small? I will take the battery and have it load tested. I will try jumping the starter one more time. I'll get the problem solved sooner or later hopefully

It's probably at the crusher by now.