I got the ring about half way off and it is still on there pretty good. Using heat gun and Blaster didn't seem to do anything so I started tapping the ring end with tiny screw driver and a pick to pry the end up. I am concerned that I am going to bend it out of round if I haven't ruined it already. There is nothing behind it, very tight fit, don't think I could get a feeler gauge in there at all. What a pain.

Bugger. Something very odd alright like the wrong ring or something we've not thought of--piston hit the head--nah won't be that. Anyway, those rings are pretty resilient so get a 20 thou blade behind it & work slowly. Only say 20 as its got a bit of strength to push with one thumb above & one below. You'd be lucky if it ends well though i'm sorry to say.

You're very patient.  Do you know what is causing it to stick like that?  Very unusual on a piston that clean.  Still wondering if someone jammed a regular ring into a tapered keystone groove which I've seen done before. 

Can you post a picture of top ring? 

Thank you for the replies. Here is a pic of the top ring.

Worth sticking it in the oven on the highest heat you can, you won't get near the 600+ degrees to melt the aluminium.
Aluminiun expands at a rate of 3 to 2 compared to the steel so should help create clearance.

I guess there looks like might be some rust on ring?  Wouldn't take much.

Heating in oven is a great idea...  will heat evenly....  just wear good gloves. 

The heat gun gets it pretty hot. Can barely touch it with gloves on. I expected it to spring outward once I started heating it but it seems formed to the piston. Actually looks pretty clean from what I can see of it so far. Lot of old 2 stroke oil solidified in the gaps I think. Inside of gas tank was crusted over with the stuff, I think it actually saved the tank from rusting out. Not sure my wife will like piston in the oven but I think we have a hot plate.

If it looks like oil, might try soaking in ethanol overnight (E85 works good if you have it near you) or maybe MEK? 

Ethanol is an incredibly good solvent and will melt old fuel and oil deposits. 

If you have an ultrasonic cleaner try that 

Haven't made any more progress yet but I found that there is a thin strip of metal behind the ring sort of like a shim running the length of the ring grove. It is totally flat so isn't a spring like you might see on an oil control ring. Anyone else see this on a stock piston before? Thank you for all the suggestions, think I am going to try soaking it some more and more heat. Hoping to salvage the current piston and rings.