[otto in norway]

What you need to to is this:

1:
After you have made a measurement of the valve overlap, at EXACTLY TDC for the oposite cylinder, make a note to how much off you are on your reading.

2:
Rotate the crank 360 degrees to TDC for the cylinder you are adjusting the overlap.
Unfasten the sprocket/adjusting assembly, and change the position of the pin. (Note the direction of adjusting the sprocket/cam for later referance)

3: Turn the crank 360 degrees to the oposite cylinder TDC (EXACTLY), and measure again. Make a note of the new measurement. Was it improved? -if so go back to point 2 and make further adjustment in the same direction. Was the lift worse? -if so go back to point 2, and adjust the other way. Sometimes, if you can't get exactly the overlap lift you want, you may have to take off the chain, and rotate the sprocket a bit (Skip over a few teeth) before wrapping the chain over it again. Then start from point 1 again.