I am changing my Brison engines from the original mechanical advance to auto advance with the new CH ignitions. After resetting the ignition timing to 28 degrees before TDC in accordance with this video from Milton, http://www.youtube.com/watch?v=GBXFpxWg7vY
I removed the button head screw near the sensor and replaced it with a ½ inch long socket head screw. The screw is jammed against the crankcase and is about 1/64 of an inch above the timing ring. I have tried to rotate the ring and dislodge the sensor with an awful lot of force and neither moved. I have also flown one engine like this for about twenty minutes with no issues. I got this method from Bill Cunningham, the founder of CH, a while ago. Has anyone else modified their Brisons this way? Dan.