Small Engines (Lawn Mowers, etc.): John Deere 68 ride on 8 hp B&S, compression

Question
Perhaps I was pushing my lil' JD too hard when taking down some pretty hefty weeds. Things were going well until I heard a "BANG" and the engine failed. At first I thought one of the vee belts broke and got caught up but on inspection the belts seemed fine. I tried starting 'er using the pull start but there was a lack of resistance and it sort of whirred for a bit but didn't catch. The rope wound back up but again it was too easy when pulled on and the engine wouldn't start.
I keep think a sheer pin or something like it might have broke. Any help would be greatly appreciated. Thanks.


Answer
Hello Bert,

Well the first thing I'd want to know is the origin of the 'bang'.  It sounds like (possibly) a 'push rod' broke off of a piston.  They do sometimes break off.

Also you mentioned after the 'bang' there wasn't good resistance (as before).  One other test you can try, Remove the spark plug and try to pull start again, this time with Your thumb covering the plug's hole. If the compression doesn't push your thumb off of the spark-plug hole then you know there is a problem with engine compression.  Did you have the oil topped up at the time this happened?  

This would be my first check before moving on to something else.

Regards,
Howard B.