if your seriously gonna try it posts pics regarding your question. but first evaluate if its worthwhile to build or if you'ld be better off getting a different engine. don't let any one stop you from trying, if you just want to say you did it, or whatever the case may be. but think about it first. cost [time and money], risk[engine scattering next to you], and reward. most verticle engines don't have a shaft that fits a centrifugal clutch so know what the rest of the drivetrain will be ahead of time(belt drive like a tractor clutch perhaps) or be prepared to machine the crank to fit a clutch or pay to have it machined. sorry for the essay but i don't want you to get in it without consideration.