Engine 'locks up' and won't turn over (crank)

[Georgia Boy]

I adjusted the valves over the past weekend. Although I didn't measure them, they well all a little loose. I would guess they were around 0.008" to maybe 0.010". I adjusted them to 0.005" at 1/4" past TDC (I confirmed this was the proper procedure for my engine from the local B/S dealer).

Since I didn't have the problem with the engine lockup at each shutdown/restart, it may be a while before I can declare victory. We'll see.

Thanks again for everyone's help.

 

[Georgia Boy]

Well just when I was ready to declare victory, it locked up again. I must have had a dozen or starts on it when it locked. After I turned it off, it sat for ~ 5 minutes before I tried to start it. The starter couldn't turn it and it took me working the fly wheel back and forth before I could free it up. But once freed, the starter had no trouble turning the engine over.

I find it hard to believe then engine would hold pressure on that piston for 5 minutes. My mother in law was using this mower and had the same problem. When it happened with her, it sat for days before I was able to look at it. So I'm pretty sure even if it (the piston) held pressure for 5 minutes, I doubt it would for days.

I believe something else is going on. Other than this problem, the engine seems to run fine. Any other suggestions?