Indeed an anti clock mag will drive the dynamo clockwise....So your arrow is correct.....BUT! if it's been fitted to a clockwise mag? Someone might have reversed the wires/rotation for the application?

The easiest thing now is to 'motor' the dynamo to check it's rotation (which will also give an indication that it's working) It's very simple and at the risk of teaching Granny and all that, this is what to do:-

Best to lay the dynamo on the jaws of a vice for stability. Connect the D and F terminals together (I've used snipe nose pliers in the two holes) now connect these to the POSS side of a 6V battery, then earth the dynamo to the NEG side of the battery. The dynamo should motor in the direction of the arrow.

Of course your dynamo might have been used on a POSS earth system? In which case it will need re-polarizing 'flashing' and might as well do it anyway before you start. The simple standard instructions are here from Lucas. Ron

email (option): ronpier@talk21.com

Also the dynamo should motor in the same direction as it is driven from the magneto when under a motor test. If it rotates in the wrong direction it can be made to motor the other way by swapping field and brush earth connections.

Thank you all so much!!!
This is very helpful. I will give it a try tomorrow!
Almost done with my 1944 BSA M20 and getting down to the last little bits.

email (option): questmasters(@)hotmail(dot)com