Hi Folks. I've put this in the 'Engine' section as I consider the attachment strap to be part of the engine, not the dynamo, and this isn't an electrical problem. Here we go. I attempted to start the latest project (Road Rocket) today and was very disappointed and somewhat alarmed that it made a horrible grinding noise which seemed to be coming from the right hand side of the gearbox or engine. It was much worse than the noise you get when the kickstart ratchet jams, more like gear dogs rubbing together, and there's nothing on the RHS of the engine that would make that type of noise. It was really loud and metallic and I was convinced it was the gearbox so.... I changed the gearbox....which made no difference at all. I turned my attention to the timing case and noticed that the dynamo had slipped and the belt was loose. Aha! Gotcha! Though I wasn't absolutely convinced that this was the culprit because there's no way a dynamo belt could make that noise. I tightened the belt and restarted the bike......same horrible noise. I don't like starting the bike with the timing cover off but needs must. As I turned the engine over slowly I noticed the dynamo belt skipping over the dynamo gear, and on further inspection it transpired that the armature was seized in the new dynamo. I had built the dynamo (as you would expect) and it was fine when I slotted into the bike. However, I remember when fitting the shiny new stainless steel attachment strap to the engine, its contour wasn't quite as accurate as an original one - no matter, it will conform when tightening it up.... wrong! The problem with the offending article is that the stainless steel strip that it is made from is thicker and wider than the original so, to get it to conform and grip the dynamo, you need to tighten it up more than you would an original. Dynamo bodies, in spite of them looking bomb-proof will distort quite easily. Furthermore, overtightening the dynamo strap can break the casting off the crankcase, now that's one crack you don't want to hear when you're giving the dynamo strap that last tweak with your spanner. As we've said many times - 'Beware of pattern parts!'. I shall be taking the inner timing cover off and fitting an original strap. Even though it isn't very pretty, it won't wreck my dynamo, or worse, my crankcases. I am amazed at the horrible noise that came out of the engine. Having removed the belt, the bike sounds fine.
