Movement or flex? I just find it hard to believe that the crank "flexes" more than it simply have movement from bearing play and what not. Flex in my mind is the bending of the crank which I just can't see happening in such a short distance , does that make sense ? Just trying to get the right terminology!

The amount of movement Roelof mentions is about the same amount as the bushing clearances from the top and bottom of the rod.

Just so there is no confusion I am not arguing the points just trying to verify them in my head! So take no offense to what I am saying.

Rick ,A lot of my experience stems from rotary engines which are not really four stroke !