Take that engine ... set it on a axis ( sideways - like the way that engine is mounted ) and watch that sucker spin sideways in a circle .
( sorry ... but it DOES happen . I JUST finished doing exactly thie with a TANAKA 16 cc engine )
Now , take the SAME engine , and place it up-right ... and it does NOT rotate like it does when placed on its side .
( tested and proved - sorry ---- need a video ?????? )
I'm not exactly sure of what your saying about your experiment. Could you give us some more specifics.
What axis's did you use in your experiment?
Could you give us some diagrams of how each axis was set up and tested?
When you say the motor was then placed upright, is that indexed around the crankshaft? Or is the crankshaft indexed to another axis?
Did the motor have a prop attached or not?
If the motor spun, sideways in a circle; was the motor mounted to anything? Or did you crank an unmounted motor and set it down on the ground?
If it was an unmounted motor, was the fuel supply kept attached?
Yes, if you have video...lets see it.