Hello Ernie;

I am doing this by moving the propeller slowly, so that the magnet passes slowly under the sensor.

Therefore this must be the position the engine fires at idle. approx 30 deg before Top Dead Centre.

Hopefully the angle is then increased when rpm increase. I dont have any advanced equipment to measure that.

But it is difficult to say wheter it is 28 or 30 degrees; 2 degrees isnt much on the wheel.

All this is based on my own logical thinking. (Which somethimes fails....)