I measured my bore and stroke one time and found it to be 69cc.
It's a Dax I bought in '14. Has 600 miles on it and got a bit faster all along the way. It's geared so tall it just purrs along, but it hits 32.6 on the flat with my big ol butt on it, and that ain't bad for bone stock. I've never taken the jug off, no porting, no fred head, kit pipe.
A 29 doesn't need a 40 tooth sprocket, but that's what its pulling.
Duane sells good engines.
It's a little cold natured on its first start of the day, probably from the long manifold I put on.
Buzz zzzzz zzz