WOW, I've officially drooled here...thanks for those pics. It's amazing to see Yamaha put that level of effort and expense in to an effectively low number of prototype engines. Begs the question who still has the drawings or CAD files to knock out a few more on a milling machine!! As grayracer mentions, in the past there were some weird builds by the manufacturers. Honda made a 5 cylinder 125 four stroke. The pistons must have looked like thimbles! And it's hard to comprehend how the weight of all those reciprocating parts and the valve gear would be an advantage when one considers the frictional losses. And there was the oval piston NR500, basically a V8 but with only 4 cylinders to get round rules. This YZM single cylinder engine is far more conventional in design but just as intriguing when you consider how they optimised it for it's intended purpose. It's great to see this sort of project and I'm certainly looking forward to seeing it come together even more so now. Cheers. Considering this IS the prototype engine that started the four stroke revolution. The return on investment is in the billions I would think now. They still can implement some things in this design into new YZ450 bikes, if they feel it worth while. Twin port exhaust, shorter rod stroke, higher compression etc. This engine has 62ish HP and higher rev limit then stock. I hope to have bike running in the next week or so. My only issue is the zeeltronic CDI. I need a startup timing map. I am using TPS and have 12 RPM points I can use.