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I've got a '98 Trail Boss 250. When I got it, it was not running. Checked the compression. No compression. I took the jug off and found a bent ring and a scored cylinder. I had the cylinder bored to 73 mm and it cleaned up nicely. I bought a Wiseco top end rebuild kit and had the cylinder finish honed for the new piston. I put it all together today and guess what.... Still no compression !!! I checked the ring gap before assembly and it was about .010 inches. Everything went together real well. I retorqued the head. Didn't help.
I started doubting my work and tore it back apart. I have found absolutely nothing wrong. Ports are clean. Bore is clean. No scratches. Nothing.
Can someone please offer suggestions? I'm at a loss. Matt
 

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Measure both the cylinder and the piston. I just had some custom pistons made for a 840 stroker motor with a turbo for an RZRS, and the pistons were seven thousands difference between the two.
 
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