I been thinking about making a little 4stroke vee twin. 60degree sounds about right. I brought home two little ryobi 25cc overhead valve weedeater motors from the scrap yard a few months ago. I will use the cylinders, heads, rods, pistons,pushrods,valves, valve covers, ignition. Make: new crankcase, crankshaft, cam, exhaust, intake manifold, flywheel. Maybe a sturmey archer 3speed hub or bendix 2speed for a transmission mounted right behind the engine. I'm starting to collect bits to use for this. My neighbor has a little foundry so I can cast the cases after making the patterns. I don't have lots of time to work on this right now...Just thinking outloud. 50cc veetwin 4stroke.
I wonder what one the 90cc chinese honda 90 copy engines would be like. I've seen for about$150 on ebay.