Timing with auto advance/retard unit.

[The Vandal]

I need to do the ignition timing on my ‘55 g3ls.

I’ve found this very helpful thread viewtopic.php?t=10853 but it talk about doing it where the advance/retard is being done by handlebar lever, my bike has the auto unit.

I think I read somewhere, something about separating that Unit from the sprocket but looking at it I don’t know of that’s actually possible.

Can anyone advise the steps that’ll be different for me doing it with the auto unit?

Cheers.

[SPRIDDLER]

Full info for setting the timing on your '55 Matchless is on page 34 of the factory Owners Manual here:

http://archives.jampot.dk/book/Owners_m ... ingles.pdf

[The Vandal]

Thanks for that link.

Next issue (there’s always a ‘next issue’ isn’t there?!) is that the sprocket and advance unit weren’t bolting on very well, I added a bit of force to see if I could push through it and, well, no.

Threads on my mag look a bit gritty and suspect the ones inside the securing ‘bolt’ inside the advance unit could do with a clean up too.

Anyone know the thread pitch so I can get a tap and die?

Should I be able to separate the bolt out of the advance unit/sprocket assembly?

[Pharisee]

Should I be able to separate the bolt out of the advance unit/sprocket assembly?

Yes... Once you have the ATU in your hand with the bolt towards you, pull the bolt towards you to take up the slack and unscrew it CLOCKWISE. It has a left hand thread.

[56G80S]

Maybe you realise this, but the ATD fixing arrangement is peculiar. You do have the washer with the slot cut out and the dished plate with two holes that fit over the pins on the ATD? If not, you will not get the secure fixing you are hoping for. Also, the bolt has a dual function, it both tightens up but also acts as a means to ease the ATD off the mag shaft; it's a funny thing with right and left hand threads, I think. The whole unit should look like this:

https://thetimingchest.com/product/luca ... 1-magneto/

Worth exploring the manual that Spriddler gave the link to and also look at the spares list:

http://archives.jampot.dk/Book/Spares_l ... ingles.pdf

for identifying other parts but don't assume that a PO hasn't made changes!

Johnny B

[The Vandal]

Should I be able to separate the bolt out of the advance unit/sprocket assembly?

Yes... Once you have the ATU in your hand with the bolt towards you, pull the bolt towards you to take up the slack and unscrew it CLOCKWISE. It has a left hand thread.

I was trying to unscrew bits of it from each other but didn't get round to trying that!

[The Vandal]

Maybe you realise this, but the ATD fixing arrangement is peculiar. You do have the washer with the slot cut out and the dished plate with two holes that fit over the pins on the ATD? If not, you will not get the secure fixing you are hoping for. Also, the bolt has a dual function, it both tightens up but also acts as a means to ease the ATD off the mag shaft; it's a funny thing with right and left hand threads, I think. The whole unit should look like this:

https://thetimingchest.com/product/luca ... 1-magneto/

Worth exploring the manual that Spriddler gave the link to and also look at the spares list:

http://archives.jampot.dk/Book/Spares_l ... ingles.pdf

for identifying other parts but don't assume that a PO hasn't made changes!

Johnny B

Yeah the slotted washer and dished plate are there, is the slotted washer meant to be dished and if so, which way does the dishing go?

I’m thinking it maybe hasn’t been put together properly previously as there is some wear inside the case.

[Groily]

Thanks for that link.

Next issue (there’s always a ‘next issue’ isn’t there?!) is that the sprocket and advance unit weren’t bolting on very well, I added a bit of force to see if I could push through it and, well, no.

Threads on my mag look a bit gritty and suspect the ones inside the securing ‘bolt’ inside the advance unit could do with a clean up too.

Anyone know the thread pitch so I can get a tap and die?

Should I be able to separate the bolt out of the advance unit/sprocket assembly?

The thread on the mag drive end is 3/8 BSF.
The female thread in the yoke of the ATD for the self-extract part is 9/16th x 20tpi Left Hand. Wear or damage there is almost always on the bolt not on the yoke and a worn one usually won't reclaim even if one has a correct and expensive die. It's always a 'replace', almost anyway.
They can be a real pain to extract sometimes because it's a poor design, relying on the first turn of the LH thread to act as a shoulder to break the taper fit. The first turn often gets damaged and the thread will not then engage in the yoke to extract the unit. They were OK when they were new probably, but after 60 years or more of use and abuse . . . horrible. And, VERY hard to extract if they won't come the way they were designed, as the taper in the inside half of the ATD prevents withdrawal 'inwards'. You'd have to drill the thing out little by little, then collapse the thin-walled remnants and replace with new. Not sure if the length of the 'bolt' for a sprocket-fit is same as for pinion-fit on other Lucas ATDs, but do know there are at least 2 lengths if you ned to replace, usually described as BSA (longer) or Triumph (shorter, because the Trihard pinion is slimmer).
They really are a PITA to play with if they have to be stripped and repaired, and there will also probably be corrosion on the central 'pillar' of the thing too, which = 'slop'.
This link from the Priory Magnetos website https://sites.google.com/site/priorymag ... authuser=0 describes in gory detail what's involved if you press the blue Link to ATD Repair . Yes, it's for a pinion-drive version, but it's the same idea. Nasty nasty things!

[The Vandal]

I see the retaining bolt on the spares service and it’s thankfully quite cheap so will have a pop at removing it, have also ordered a tap and die in the appropriate size so can just them down the two parts and see how they go together.

[The Vandal]

If I have borked my auto advance unit, is there a cheaper manual option that can be fitted?