How is it known that it is not firing on No. 1? Does the engine run the same with the No. 1 wire disconnected as it does when the wire is connected to the sparkplug? Does the timing light fire when it is connected to another cylinder, such as No. 6, which is 360 degrees after No. 1? Try using a plug and wire (of the appropriate length) that are known to fire ok on another cylinder.