I need help, I'm planning on building my own 100cc or 150cc 2 cylinder gasoline engine. Yeah I know I could just take a DA or 3W and copy it but I want this to be mine. I have access to a machine shop and all the related tooling and plenty of help with the actual work. What I need help with is design. Should I purchase commercially available cylinders or make my own. I plan on grinding my own crankshaft and milling my own crankcase but I need guidance on the diameter of the crank how many bearings? I plan on using a Walbro carb and CH ignition. Do I turn my own pistons what kind of bearings on the connecting rods? You see I have many questions and any help would be great.
Thanks
RT

Sounds like an exercise in futility to me. All that time wasted on machine work when you could waste it building airplanes. Go figure!

If I were going to do this I would use other peoples experience and benefit from their mistakes. Don't re-invent the wheel, someone already made it. Get shop drawings of several engines and make yours using the ideas in the drawings. Don't have to copy anyone but you can see how they did it.