I would be reluctant to mill anything until it's running as it should or you may end up having to start again with a new cylinder & piston.
Did you vac/pressure test it after you built it?
We're the parts all new?
What was your procedure for restarting it warm?
If it idles down & dies it could be a bit rich on the low side, if that's the case it should restart fine with a bit of throttle & will then smoke for a second.
Clutch/drum shouldn't need roughing up but I'd check they are clean (clean with brake parts cleaner).
Is it oiling well?
Does the chain move freely on the bar?
How is your chain sharpened? (Pic's would be good)
I believe you, and agree with you and would tell anyone else exactly that. I was just plain too damn excited to not. I am running 32:1 (it might be a little bit oilier than this, and that is maybe also contributing to difficulty getting the carb set correctly because of a lot of oil in the mix?) and I did inspect the piston after a short run and no scoring. I'm also only on 3/4 throttle. My hope is that those things combined will have allowed me to make that cut without major damage.
I did not vac or pressure test it, I don't have a vac pump, I have a bike pump but hear that that's not a good way. It builds pressure when turned, and the decomp is pressurized, but I'm guessing that doesn't say anything about how MUCH pressure or whether there is a slow leak?
All parts are new, case and crank were per-assembled, I swapped out OEM flywheel key, throttle rod and have an OEM trigger and choke selector rod coming in. Bar is a new Forester.
For restarting warm, very soon after running (under a minuteish after shutoff) it will restart on ON, longer than that I've been setting it to the warm choke start. It seems to need the warm choke start, as that is also what has had more success starting it cold. If it popped two pulls I'd move it to ON.
"If it idles down & dies it could be a bit rich on the low side, if that's the case it should restart fine with a bit of throttle & will then smoke for a second." Now this seems likely, I believe this could be why it starts more reliably on the warm choke setting. If low is too rich, I want to tighten the L screw 1/16th turn at a time?
I will pull the clutch and clean it and the shoes well with solvent.
It oils well, I throws a good spray. I use veggie oil, chain moves freely and the groove and DL have a film of oil.
The chain is a Forester, full comp rip 3/8" .050 gauge. it's as is from the factory. I can snag a picture if needed.