I just rebuilt the top end on a 2003 Honda rancher 350. I replaced the cylinder head, the cylinder and bought a piston kit from Amazon the niche brand. I've always had good luck with the brand. Here's a little bit of what's going on. I rebuilt the top end a few weeks ago and the bike sounded awesome, I realized I had to replace a few cables while I had it all apart. So I got all the cables. I replaced them started the bike up and I get this noise. Any ideas what it could be? I have already torn the top end off to evaluate to see If it was something that I did during the rebuild and everything looks fine except this on the piston and cylinder. Any input would be greatly appreciated on this as I bought this ATV from a customer and was hoping to fix it up to have a second quad. I have rebuilt many of these top ends on these bikes with no issues. I ended up getting a replacement top end under warranty as that's the only thing I can think of is possibly a extreme piston slap. The connecting rod was tight like it was before I rebuilt it. Here is a video of what it sounded like before I tore it down.