Magneto Installation

[flyingriki]

I know most will say get another P-MAg, but here goes:
I have one P-Mag and one Slick. Why is it when the mag is pinned correctly and stabbed at exactly 25? BTDC (per my engine), that it still takes a LOT of movement of the mag to get it timed correctly?
Seems like it ought to be almost perfect. Did it twice and both times it was way off. Pin was set correctly, engine was set correctly on compression with no lag in the gears. I'm stumped......
Thanks!

[aerhed]

If you lightly play with the drive gear while the pin is in you'll notice almost a tooths worth of play. Don't use much turning force while pinned and, of course, after seating the mag don't rotate it or the prop before pulling the pin. Also, to get any kind of accurate timing you have to set the mag then back the prop and bump it forward for the break. Otherwise by trying to turn the mag to the timing light the accumulated slop will get you.