A couple of years ago I built my first IC engine and my son really likes it so I thought that I would make him one for Xmas. There are no plans, I just made it up as I went along. I hope to make a few improvements to fix some of the things that didn't turn out as well as I would like. Some of the basic specs are: 21mm bore with O ring, 36mm stroke, 8mm fabricated crankshaft, 10mm plate crankcase, 50 mm cylinder, ball bearings on crank and big end. This would be a good first engine for anyone who wants to build along with me because I don't care too much about accuracy, if one bit is the wrong size you just change the next bit to suit. (Cylinder needs to be close to o ring size). build it in imperial if you want.