dependng on all the circumstances, altitude, accuracy of the gauge, whether or not you held the throttle wide open while checking just to name a couple. 150lbs sounds kinda low for a modern mx 125 to me, not nesseceraly bad but low. Plus if it had a a cast piston in it they will tend to crack the skirts off more than a forged piston when they get old.
if and when you take it apart and you see broken things something worn past its limits is probably the culprit, if it is blue and seized/welded together lack of lubrication is most likely the culprit.n Unfortunately most of the time when you take something apart after a catastrophic ending like this you will find broken and blue parts .
Jaybird, any insight on the compression readings for a 125? this is something that I believe you would have a lot more info on than me.