I adjusted the mag timing today for the first time. I read some articles and watched some YouTube videos to learn the techniques. I bought a buzz box at Aircraft Spruce and attached the green and red leads to the magneto P-leads and the black wire to ground. The left mag fired a bit early so I adjusted the mag by loosening 2 nuts that hold the mag housing to the engine. Just moving the housing a bit and you can fine tune when the light goes out and box starts to buzz which indicates the mag will fire the spark plug. I made sure that this happened at 25 degrees before top dead center of the piston. You must also be careful when you are tightening the nuts on the mag housing that you don't inadvertently move the housing which will throw the timing off. Once I was happy with the left mag I tweaked the right mag to fire exactly the same time as the left mag. I also replaced the lock washers that are used to attach the mag housing. After I was done I pulled the plane out of the hanger and started the engine and checked the mags. Everything functioned properly.
