Having difficulty refitting auto-advance unit on my 1957 Bullet. You may have seen from previous posts I had the magneto repaired and am very much learning (or not) as I go along. My auto-advance unit has a single bolt running through it given its a 1957 bike (later versions I understand were modified) which is tightened up anti clockwise to pull the unit off the magnet (Lucas SR1) shaft through an external thread but tightens up clockwise onto the magneto shaft itself by way of an internal thread inside that bolt. This combination frees the auto-advance from the magneto. I am wondering in refitting do I remove the bolt from the auto-advance unit completely and then push the unit onto the magneto shaft. Once it is locked on by this means (as I am assuming in suggesting this there is some sort of inner ridge inside the auto advance unit to match the magneto shaft somehow)) do I then reinsert the bolt and tighten up clockwise? Sorry if this makes little sense to those more mechanically minded than myself but have tried leaving the auto-advance fully assembled with bolt installed but its very loose and even if it binds on the magneto shaft it spins the magneto rotor, won't tighten and disturbs the timing set up as advised in my workshop manual. This states set the points gap at 0.12 and then advance the cam clockwise to about 2 thou when the feeler gauge will just pull out. Auto-advance unit secured to fully advanced with engine 1/2 inch before TDC. All my timing marks on the relevant wheels are then lined up. The manual is unclear as to how to refit the auto-advance it just says try to avoid the unit slipping on the shaft. I know i could try this without asking but don't want to damage anything given the age of the parts. The magneto had failed so at least in taking it off have solved one problem to create for me another. Any help appreciated as usual. Trust you are all keeping well in the current situation. Hugh
Hi, check that the thread is not stiff. just hold the rotor gently and the auto advance should just screw up with you fingers and finally tighten with a spanner. It sometimes is a three handed operation. Remember to take up any backlash in the timing gears. You may have to take several attempts before you get the timing correct. I take it this is an SR1 magneto? Vince
I bought an otherwise good SR1 mag where the 3/8" BSF thread on the drive end of the shaft has been a little bit chewed, and it will need cleaning up with a die or die-nut before the auto-advance unit I have for it will fit properly. Might be worth checking the thread on your SR1 too in case there are any burrs or snags. Check the internal thread of your auto-advance unit too, in case it needs cleaning up with a plug tap.

As you managed to get the magneto off for reconditioning I doubt if it's too bad, though

I may not be understanding your problem correctly - but I had an issue where the nut bottomed out on the shaft and became tight but it still allowed the ATD to rotate on the shaft.
This was because I didnt fit the 'C' clip washer!
you could check that the tapers are not damaged or burred which would prevent the ATD from 'locking ' onto the shaft.
have you tried fitting the nut onto the shaft without the ATD? it should go all the way on with just finger pressure of course. if it wont go on with fingers then do what Adrian suggests.

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