I feel like an idiot for having to ask, but at a rummage sale I ran across an old NOS Honda piston in most of it's original box. Wouldn't you know, the only part of the box missing was the top flap:doh:, where they used to put the doggone part number. For 25 cents I couldn't leave it there. Now, I have this piston and no idea what it fits. It measures about 50 mm across at the skirt, and 50mm tall. It has "N1" and ".5" stamped on the crown, so all I know about it is it is a honda four stroke small bore 5 thousands over. Has to be from the 60's or at latest 70's judging by the box. Any ideas? A 90cc? 100cc? Thanks!