I did a 50cc cylinder a decade ago:
http://team-nerdspeed.blogspot.com/2009/07/custom-cylinder-cast.html
And I've been working on a 75cc direct replacement for the Gilardoni cylinder, except more ports, bigger transfers and more aggressive port timing figures. I poured my first test on Sunday, which I thought was a total failure. I cracked the mold yesterday and it turns out it was a failure, but not by much. I'm going to make some changes to my burnout process and mold design and try again soon.
I mostly update my instagram @joshspaceman, but figured I should share here as well.
