They do sell inch sizes at home centers in Japan... You could also try an automotive parts supplier. They are located all over the place.
PS: Found one at Amazon
http://www.amazon.co.jp/KTC-9-5sq-ロングヘキサゴンビットソケット-16inch-BT3-3/dp/B002NK3FKW/ref=sr_1_4?s=diy&ie=UTF8&qid=1408516993&sr=1-4&keywords=3/16 inch
Holy cow dude how did you find that?
I did look, honestly but I could not find that one, wow, I'm impressed, I just ordered it, Domo!
I did get the darn cylinder off, finally!
My addled brain remembered that one of my woodworking tools, an Incra Jig, uses inch stuff, and they include this long 3/16" hex screwdriver tool. I have two as I own two Incra jigs, so I took the plastic handle off of one and stuck it in a 5mm socket, then I put a big half inch drive breaker bar on that the clamped the whole saw in my woodworking vice, fingers crossed and pull, carefully..... "Ping" goes each hex bolt in succession, and I'm free and clear!
The piston has a coating of carbon in it.
I think the piston is in fair shape, considering this is a 38 year old saw.
Some blow by, I guess I'll be looking for new rings for this piston.
I cleaned off the carbon and the top has "N5" and "B" stamped on it, as well as the arrow pointing towards the exhaust port (?)
The intake side of the piston, no real scratches, just a mark there that will come off if I hit it with the green scrubby pad some more, I think.
The exhaust side of the piston, these are the worst scratches I can find, I think this will be OK to reuse.
The top of the cylinder was also coated with carbon, the cylinder itself looks nice and clean, no scratches etc. The carbon was quite built in the squish band area, as well as around the spark plug hole, that is all gone now, and it is shiny and clean.
So I'm thinking that I should replace the bearing on the wrist pin, while I have this apart, replace the piston rings and then put it back together. The gasket on the base looks OK, but if I can get another one I should replace that too, right?
Thoughts?