In addition, Atlas came with a end of camshaft timed breathing, Competition magneto as standard, as well as other differences.Model 99
Displacement 597 cc
Bore 68 mm
Stroke 82 mm
CR 8.2:1
Model 650
Displacement 646 cc
Bore 68 mm
Stroke 89 mm
CR 9:1
Model Atlas
Displacement 745 cc
Bore 73 mm
Stroke 82 mm
CR 7.5:1
Oophs!!Almost correct, except that 650 and Atlas has same stroke, 89 mm.
SameCams?
The basic NHT castings are the same from 650 1960 on. This may not consistent for 500 or 600 based on production rumors.Where does the Mercury engine fit into this? (1968-1970).
The cases are stamped 650SS, but I keep finding references to how elements of the Commando bottom end were introduced. But I am not sure what.