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98 Cr125 piston trouble HELP!

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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. ImageUploadedByThumper Talk1427765366.217202.jpgImageUploadedByThumper Talk1427765405.449375.jpg

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Do you have any pictures of the cylinder & head? The damage on the top of your piston looks like the crank bearings are failing. The bearing cage starts to break up & the pieces will come through the ports to the top side of the piston. Sometimes the pieces blow out the exhaust & sometimes they get pounder into the piston & head which looks like the damage you have.

If the crank bearings are so bad that they are coming apart, the crank seals will more than likely be junk & cause an air leak.

Take the ignition cover off & lift up & down on the flywheel. If you can feel ANY slop, your bear are junk.

The connecting rod lower bearing can also be coming apart. To check the rod bearing, slide the rod against one side of the crank & lift up & down. If you feel play, the rod is junk & the crank needs a rebuild.

If you get this deep into the motor, rebuild the complete rolling assembly (crank, main bearings, piston, piston pin/bearing, engine seals & gaskets). Make sure the cylinder is in spec or you may need a nickel plating job.

Sorry it's not the best of news.

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As KPRacing said, either your crank bearing sh!t the bed, or some foriegn matter came down  through the airbox/ carburetor, and caused the damage.. motor needs to come apart..

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Thank you for the responses. But the top of the cylinder has like the same "pattern" as the top of the cylinder head. Would that in someway be related?

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As KPRacing said, either your crank bearing sh!t the bed, or some foriegn matter came down through the airbox/ carburetor, and caused the damage.. motor needs to come apart..

I have not yet checked the reeds to see if they have broke and are not sealing.

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Thank you for the responses. But the top of the cylinder has like the same "pattern" as the top of the cylinder head. Would that in someway be related?

its identical because whatever was bouncing around in there was hitting the piston then going straight up to the head.

 

either way, you need to tear the whole motor apart to make sure no pieces are left in there, even one piece is waiting to take a new top end out.

I have not yet checked the reeds to see if they have broke and are not sealing.

any air gap or small crack/chip means replace them.

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its identical because whatever was bouncing around in there was hitting the piston then going straight up to the head.

either way, you need to tear the whole motor apart to make sure no pieces are left in there, even one piece is waiting to take a new top end out.

any air gap or small crack/chip means replace them.

Alright thank you for your time and advice, i will look into this further.

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