I just cleaned up a Polini 208 piston that looked much worse than that, and it runs very well now. I was advised to use a fine file - no emery/sandpaper as apparently particles can lodge in the aluminium and are pretty much invisible. Just take off any high spots... you have nothing to lose.
That piston will go again. I apologise but have not kept up (sorry). Is the 'Pig' rotary induction or reed? cos if its rotary, I'd be more concerned about the condition of the sealing pad than the piston to be honest. If reed, then a good clean, you'll be ok. Take main bearing out to clean, or preferably replace it.
Additionally, when you order new seals, order Viton double lip, not 'genuine' as a LOT are being affected by fuel.
Oh, and yes, seen lots like it, normally runs weak/ smokey before it gets that far though.
Simon.
Fortunately the casings are LML reed, Simon. It's always been a bit smokey, put that down to running on 3% though and we'd just changed it up to an Si24 and been run for a couple of weeks. Luckily when this happened it was ticking over on the stand, it just stopped ...clunk and the K/S wouldn't go down. I suspect the spring had gone sometime before, there wasn't much oil when we drained the gearbox to split it either.
I've got a new piston in stock but I might see how this one measures up now I've taken the high spots off.
"Our dilemma is that we hate change and love it at the same time; what we really want is for things to remain the same but get better."