Hate to say it but sometimes the piston pin can get so corroded to the connecting rod and it just wont come apart.

I had an OS 52 Surpass and a 70 Surpass that did that. I soaked each in a crock pot of antifreeze for a few days (now use ATF), soaked in acetone for weeks, 30 minute bake in a 300 degree toaster oven, even a small torch. NADA!

I finally cut the con rode with a dermal tool so I could get the engine apart. Once the piston was out I was still unable to press the pin out of the piston! In the end I damage the piston as well and needed to replace all three parts.

I think part of the issue is the fit between the piston and the liner doesn't really allow all that much liquid to get in to the pin to break up the crap that builds up, not to mention there isn't much room in there to begin with, and if the corrosion isn't able to be dissolved the parts will never come apart.

Right now I have a K&B 61 now that's in the same boat. Not even sure parts are available for it so its just sitting till I can come up with something new.

Bill S.