Norton Dunstall 810

[Atlas]

Is anyone familiar with the 810 Dunstall Norton motors?
Have just been putting one together and was rather surprised that the circumference of the pistons are approx 3mm down the bore.
Almost as if the standard 750 norton rods are too short! At least the piston to valve clearances wont be an issue.

[Motu]

The 600 engine had a shorter stroke,but I doubt if someone would put a short stroke crank in....was more than 3mm shorter anyway.The Atlas had concave pistons,but the compression height would still be the same.So - time to do some measuring of gudgeon height and rod length to see where the difference is.