So that you get rid of the doubt next photographs with accurate data :
Diameter popped 75 mm , diameter piston 76.5 mm
Right now are you shure ?? Any washes.
Weight popped 75 mm 1000 G
weight piston & rod 76.5 mm 850 G
weight popped 62 mm 400 G
weight piston & rod 62 mm 370 G
But the window of the flight of the valve of 75 mm is only 64 mm, what is very similar to the window of the flight piston 62 mm .
That is it results from it that the valve of 75 mm is giving the same flight as the piston 62 mm that is 1000 G to 370 G !!!!!
==~~ 2.5 more weight popped to piston& rod !!
It only looks impossibly. but this way is.
In principle ,for them greater popped/piston diameter, it is this difference in weight will be to the benefit of pistons.