250-500cc Piston movement in bore

I've noticed the last couple of times riding my bike, it seems to be down on power. I did a compression test and with the race head, it has 180psi. I never checked it when it was new or did the head swap. I checked the power valve and it is right at 50.5mm. I did notice a good sized dent in the head pipe that I don't remember being there, so that may be the culprit. However, with the head off, I was cleaning the very little bit of carbon it had on the top of the piston and noticed I can turn the piston on the rod axis a tiny little bit clockwise and counter clockwise. Is this normal or maybe a worn piston pin bearing? Also, I noticed the power valve was pitted, is that normal?

So I decided to take the cylinder off to investigate further. There doesn't seem to be any up and down movement in the rod bearing but it does move side to side. Normal? Also I had my dad measure the piston and bore since he is a retired machinist and came up with .004-.005"(0.1016-0.127mm) clearance. Bore is 72.021mm. I can't find my Husky thumbdrive manual and can't download a large file because of my molasses internet. Sounds excessive to me. Ring gap is .0033"(.0838mm) for top ring and .0024"(.0609mm) for the bottom ring. Time for a new piston and rings?

Well, I hate to second my dad, but he is 79 years old and the piston and cylinder look great, so I was having a hard time accepting the wear. I went and remeasured the piston and cylinder and got .002 clearance and I'm just going to order some rings and get the 11 dents taken out of my pipe. 10 of which are in the head pipe area.

Rings and PV springs and check the reeds is about all you can do short of an overhaul. I would be interested in the compression number after the ring change.

Stock or forged piston in it?

Forged pistons are made with a little more clearance because the piston expands when hot.

The side to side rod play is normal.

Usually a 2 stroke will get rather noisey as it wears.

Confused about your ring end gap....s/b .006-008 per inch of bore if I remember correctly for 72mm it would be like .018 to .024". Are you sure you have .003 of ring end gap.....sounds tight. Maybe you have .033"?

Stock piston. Yes I accidentally added an extra zero in there.

Okay, so maybe the rings are worn a little....just a little.

Put the new rings on a see how it runs.

Actually the "safe" rule of thumb for ring-end gap is .004 per inch of bore, and for most MX/offroad builds I prefer .003/inch. Most piston manufacturer's don't even give you that option, though, as the ring will have at least .004/inch on a properly clearance bore, which I find VERY annoying but they know 90% of people don't bother to check ring-end gap and the manufacturer errors on the safe side.

Well, I figured it out. When I was cleaning the cylinder before reinstalling it, I noticed some light in the reed cage. Took them out and there was a good piece of a corner missing off of one of the reeds. Installed new reeds and it rode great today.