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I'm now convinced the part you're describing is indeed the advance and retard arm as you mention there is a sleeve which spins on the rotor body. For those that might be interested, this is the advance and retard mechanism for this bike. Typical of early car engines the timing cam was directly driven from the crankshaft. which meant the faster the engine went, the faster the timing shaft would spin. If the contact breakers (points) were fixed in one position and opened & closed accordingly, as the engine speed increased, the engine would not run properly as it would'nt be able to 'keep up' with the speed of the shaft. It was discovered that if the points were 'moveable' then they could be adjusted to open at a different position relative to the position of the cam. On a points based ignition system, the timing of points opening relies on moving mechanical parts to contol the opening and closing of the points. In an early 1970's car with an early LUCAS distributor, the points are attached to a moveable plate which is moved by centrifugal forces and is also attached to the vacuum of the carb. The faster the engine went the forces would move the plate altering the position that the points open. With a motorbike from the same era, there is not enough room to fit all these moving parts, so they created a system which moved the position of the engine cam instead. Here on the Yamaha DT of 1974, the points are mounted in a fixed position on the backplate. Unlike a car the backplate is not adjustable with this setup. Yamaha subsequently came up with the idea to advance and retard the opening and closing of the points by altering the position of the engine cam. In this case a sleeve which can be moved on the magneto body. Centrifugal forces makes the free moving sleeve spin faster, the arm and spring hold it in check, but in essence the position of the cam, when spinning faster, will cause the points to open sooner or later (depending on engine speed) Which hopefully answers your concern from your first post Doug:- No it can't be in a 'fixed position' otherwise it wouldn't be able to alter the timing. It's designed to move... but not by much. Hope this helps. NE0

It's a wierd bug... Not something I'd generally expect from Invision. The problem is that the 'Contact Us' link takes you to a board based emailing system, which is of course also affected by the bug, so is rendered useless. There are a couple of options... 1/ When sending PMs, the message field is REQUIRED to have text in it (I'm moderately sure that when this bug appears, you can still type in the 'title field'). If the requirement for for text in the message field was removed, it would be possible to send a PM with only a title (thus still getting a 'IT DOESN'T WORK!' message through! 2/ Add a 'forums trouble' button in the 'Contact Us' window. That shouldn't be too hard to implement! So instead of sending a mail, it just sends an automated message to whoever stating that there are forum issues...