I've built the one in Rick's second post. That was about six or seven years ago, and it ran very well after some fiddling around to get rid of drag. I say "ran" because I had it at work with me one day and a co-worker knocked it off the bench, and the concrete floor didn't do it many favors
Anyway, after a going over, it runs once again; but not like it did. The flywheel has that annoying wobble in it still (I think the hub has been bent).
I'm not sure if the drawings posted for this engine have all the dimensions on them. IIRC, I had to work some of them out on my own. With a little attention to details, you should wind up with a good runner though.