I don't recall the bar/stem size I have but I found one to fit the stem I had which is a standard 1 1/8" mountain bike stem.
Doesn't that engine have a built in transmission, Im pretty sure they do and you should just use that.I am impressed with this setup! It makes me want to lean more towards a shift kit now, would that be logical for my engine? I'm sure I could shim the clutch springs in my ATC70 clone so it grabs at low idle like yours.
http://motorbicycling.com/showthread.php?t=57388
I haven't been here in a while but yes it was finished a very long time ago. Im about to post an update.Wild Bill did you ever get your MTB with the jack shaft done YET . It's 2-28-2015 I would like to know how it worked out for you.