So I've had a cr 125 for a while now and came from a yz85 so I'm pretty familiar with the basics on the 2-smokers. I ordered a piston kit for it. As the previous one lost compression, and it was a normal rebuild. I took the top off and the piston had the ring seized to it. (This was the old piston). So I took off the cylinder popped new piston and put it all back together, started up just fine radiator fluid and everything. Ran through the heat cycles that night, changed the oil, ran 32:1 klotz through it for the rebuild. I started it today for two minutes this is an extra caution. And about 2 1/2 half hours later went out to go ride. It was running fine for 3 to 4 minutes and then it suddenly just quit. It WASN'T a sudden stop like something snaped in the engine. Was more of a "ran out of gas engine slowing down stop". So I pushed it all the way back to the house. And pushed down on the kick starter and there was literally no compression. And five minutes before it was hard to push down and had plenty of compression. I checked it the spark was tight, it was. The water impeller for the radiator system was NOT stripped and worked when I pushed down the kickstart. So the only other thing that my buddy said it might be is some kind of bottom end seal that is letting air in and burning up the piston. I'll include a picture of the first piston below. So I just need some answers. Thank you in advance for any solutions.