New top end,now it's rattle

[Zio7]

Hey Guys I put a new top end in my 88 yz 125. I bike ran fine before the new top end, just was a little down on power. I put the new piston in with a new top rod bearing. The ring gap was perfect and I honed the cylinder just to get some cross hatching. Well the bike fired right up and ran great. But then I noticed there was a tapping/rattling noise. It sounded like piston slap. I took it apart today and there was obvious wear line on the left side of the cylinder. I thought it was from the wrist pin but that was tight and the wear mark and wrist pin do not line up. The only mark on the piston is a little scuff at the bottom where it was wearing on the cylinder.

I am totally lost as to what caused this problem. If someone could give me some ideas that would be great.

thanks
Tom

 

[IZ 250]

my 250 has the same rattlin noise and that scratch. I wouldnt worry about it if everythings tight.