Note the additional single hole, 180° from the weight and further out on the diameter.
It is convenient that there is, or just happens to be, a hole opposite of the counter weight, but perhaps that's a corrective measure in attempting to achieve the proper imbalance for the intended application?
![Undecided :-\](http://fepower.net/simplemachinesforum/Smileys/default/undecided.gif)
But still, aren't we just guessing, or perhaps even assuming?
![Roll Eyes ::)](http://fepower.net/simplemachinesforum/Smileys/default/rolleyes.gif)
Scott.