Bonneville America Forums Forums General Motorcycle Forums Other Bikes 1971 Triumph Bonneville 650cc

Cams can be a problem for those not used to working on those since the cam gears have 3 keyways and you only use one. The seal behind the points that seals the end of the exhaust cam is also a common problem on those. They had a tendency to leak after a while and needed replacing to keep the points dry. I don't see the cams being the problem if it won't stay in time unless the taper on the end of the exhaust cam is worn or the taper on the advance unit is bad. I don't remember what year you have but the earlier bikes didn't have a notch in the end of the cam or advance unit and you had to set the bike up in firing position and put the advance unit in so it allowed you to set the points. If you didn't get it right you had to pull it apart and try it again. Not to hard once you are used to it but first time can be a pain. Also I have worked on bikes that a bolt that's too long was put in to hold the advance unit allowing it to slip in the cam. It won't stay in time then either. It looks like it is tight but is actually bottoming out in the cam before it tightens the advance unit.