Ok checked the voltage out put on my mag. as instructed here on the forum. I have about 7-8 volts at an idle and the light is a little dim. When I throttle up I have about 15 volts and the light is very bright. I took the lid off the coil box and watched the coils while running on battery. On two of the four coils I could actually see the bottom point bridge vibrating. On the other two I could not detect any vibration. On mag it was hard to see any vibration in any of them. I am thinking I must have coil problems. All four coils have been recently rebuilt and adjusted on a coil tester. Engine ran fine first couple times out but then all of a sudden started running rough on mag. Is there something in the adjustment of the points that I may have missed that would let it run fine for just a short period? Thanks

What kind of coil tester did you use?

An original hand crank magneto that is being used on a regular basis in a shop. I have no doubts about the tester being correct