New AAU

[Mikey82]

The replacement auto advance unit that came with my refurbed k2f magneto ( as the old one was a steel aau and heavy so could damage the bearings) has a fibre gear, so to fit it is slightly different to the old one.
What an absolute pain to fit, trying not to move points, whereas before it was slowly fit and tighten bolt now it’s pull unit towards you whilst pushing bolt in…. then find the bloody points move I’ve given up for today 🤬🤬🤬

This is the fitting instructions
Fitting note: screw the centre bolt on to the shaft at the same time as you gently fit the unit on the taper, if you fit the unit first then attampt to tighten the bolt it will lock up.

It’s harder to fit than the old one 🤬

[Triton Thrasher]

You have the nut screwed most of the way in, with the pinion loose on the taper.

When you have the points just opening with the crankshaft in the right position, you press the pinion onto the taper and tighten the nut.

Then you recheck the timing.

[a101960]

Steel? I've never encountered steel. When I replaced mine I bought an aluminium one from Tony Cooper the magneto repairer in Halesowen. I chose aluminium over fibre because of their reputation for shedding teeth. The fibre one fitted originally on my magneto was on the verge of doing just that. I'm not absolutely certain, but I'm pretty sure manual advance units were fitted with ally drive wheels as standard. Of course you may know better.......

[trevinoz]

Manual gears were originally fibre.

[Swarfcut]

 The Prince of Darkness strikes again.

 To add a little more detail to TT's excellent concise post. Looks like you have an ATD with a good working self extracting function, making assembly slightly different from the earlier example.

    The original centre bolt has two threads, normal internal right hand to secure the bolt to the magneto armature, but also a left hand external thread to act as a self extractor mechanism for the ATD. So at some point both these threads will be engaged when removing the ATD but this is not needed when assembling and is the cause of the problem.

 Extractor function was all fine and dandy when new, but like most folks I've never been able to get this to work....the extractor thread is only a few threads deep and  invariably won't engage. We're talking well used parts here...

  On assembly the trick is to make sure the centre bolt is screwed into the ATD past the left hand thread, the bolt will be completely free, then fit the unit to the magneto and push onto the taper as the centre bolt is turned as normal. Just before the tapers engage, the armature and timing gears are checked for correct positioning, engage the tapers, tighten the bolt.

 Don't forget timing is set at full advance, wedge the weights fully open. Service Sheet 203 gives the procedure.

 The fitting instructions you have indicate that unless the bolt is past the self extracting LH thread, it's function will come into effect, locking everything. But on the face of it, this is not well explained.

 Fibre gears were always the original fitting, quiet running and fail safe if the magneto seized. Aftermarket Alloy gears were available in the '70's, my example needed a fettle to make the teeth mesh nicely, followed by extraction of lots of Aluminium swarf from the sump after a run round the block. Be warned.

 This link from Priory Magnetos explains it better than I can. Thanks Andrew.

  https://sites.google.com/site/priorymagnetos/atd-units

   With old worn parts  it can be a common problem, try this from a while ago.

 
https://www.a7a10.net/forum/index.php?topic=18088.msg157061#msg157061

 Swarfy.

[Mikey82]

Triton Thrasher and Swarfcut Thankyou for the advise a lot easier to understand and it’s worked.
 I can now fit the AAU 👌👌