Following RF Whatley's 'Timing BSA Singles' instructions (excellent document), I found it very hard to manually turn the AAU counter clockwise to full advance when timing the engine ignition after removal and re-installation of the AAU and prior to tightening the retaining bolt. There is undoubtedly a special tool to do this, but in lieu of a tool, I decided to make my own. It took about 15 minutes to make out of a short length of 1/2" Type L rigid copper tubing. I used a hacksaw to saw most of the way through the tubing at one end, leaving one small piece sticking out approximately 1/16 inch and about 1/8 inch wide. I then filed the remaining tab down until it perfectly fit the notch on the lobe. The 1/2 inch copper tubing is an almost perfect fit for this task and is soft enough to easily saw and file.
Current Bike: 1968 Triumph Bonneville T120R, 1969 BSA Victor Special, 1975 Norton 850 Commando John Player, M1030M1 U.S.M.C. Diesel Previous British Bikes: 1968 BSA Lightning, 1969 BSA Lightning, 1969 BSA Firebird Scrambler, 1972 BSA B50 Gold Star, 1974 Triumph Trident Previous Non-British Bikes: 1983 BMW R80RT