Quote Originally Posted by odd one View Post
Very nice. Did you drill the ports after it was all assembled to ensure accuracy on alignment or were you good on your calculations.
The calculations are quite easy as the ports are on the same radius for the cylinder and valve plate. Once I had those arcs I then constructed a line that goes through the crank pin (when it is at both extreme positions) and the centre of rotation of the cylinder on the valve plate. All of these points are quite easy to calculate.

If you look carefully at the exhaust ports on the valve plate you can see that I enlarged them, effectively allowing them to open earlier - so I guess my calculations weren't spot on.....