Gentlemen, Thank you for your suggestions. The bike in question is a 1970 750 with single phase two-wire alternator, Norbsa your observation that swapping the alternator wires can affect timing is an interesting one. From a brief look at the wiring diagram these two wires simply go to the rectifier and according to Roy bacon's 'restoring motorcycle electrics' they can be connected to either of the outer two spade-connectors on the rectifier. Additionally I could actually run the bike without the alternator even connected and simply rely on battery power until it went flat. However I will certainly try to reverse the alternator wires when I have my strobe connected and see the result. The site where I saw the innitial reference to swapping the two wires from the ignition pickup is 'britcycle,com' (british cycle supply company) in their section on 'Boyer electronic ignition troubleshooting' and this guide is purported to have been supplied by Mr Boyer himself. Ron, your comments about possible timing anomalies are well taken, my first inclination was that I has cocked something up (many years of experience and expertise in this area) however I am lucky enough to have another almost identical bike in my possesion so I do have a reference point. I set the bike to TDC with a dial guage removed the rocker covers and noted that the valve timing was as it should be. I then checked with a dial guage on my reference machine how many mm before TDC equated to a specific position on the primary cover degree indicator - this turns out to be 3mm BTDC = approx 20 degrees and 4mm = 25, my guage has insufficient stroke for further measurement (why is it that in life we could always use just another inch or so?) - So both bikes indicate the same data. I have also run all the actual components of this ignition system on the other bike with no problem at all, so it is a bit of a puzzler. My next step is to strobe the ignition to get a visual reference point from that and then swap wires from the ignition pickup and see what happens, I will then do the same excercise with the two alternator wires. This forum is trully excellent for sharing this kind of information and I promise to post the result of my investigations regardless of how much egg eventually ends up on my face.
Dave