Can't get my magneto off - help!

[Simon59]

I’m trying to remove my magneto, (1955 A10) which has the automatic advance inside the drive pinion. I know that the nut is supposed to act as an extractor, to get the gear off its tapered shaft, but it just turns and turns. I’ve tried everything I know – replacing the three magneto nuts (including the long one) to give the extractor something to pull against, putting a lever behind the nut whilst turning to encourage it onto its extractor threads and tightening it back in and trying again. In your view, do I now need a puller to get the gear off? There doesn’t look like there’s much room to get one in… Any hints and tips much appreciated.   

[edboy]

hi,
the tapers arnt generally that tight. i would remove both springs, extract the lht bolt and use 2 hefty screwdivers or prise bars to lever behind the metal centre where the bob weights are. and bobs you uncle.

[chaterlea25]

Hi
In a situation like this I have removed the three nuts, loosen the  centre bolt one or two threads
push the mag and  ATD back against timing case and smack the centre bolt head

No liability accepted with this "method" 

John

[muskrat]

I was thinking that as well but have only had to resort to that with a manual advance type.
Cheers

[Simon59]

Thanks guys, I know I can rely on you for some possible solutions.

After more turning and levering, the nut came out, and as you can see, the external threads are all but gone.

So I might screw it back in and give it a whack, sounds like it might work. Maybe a tap or two first?

The other thing I thought of was to buy a new nut, screw it in and then unwind it to (hopefully) release the gear.

One way or another, I need my magneto off!

[groily]

Pretty well done to get it out I reckon. As you can see, a really lousy design, relying on the first turn of raised lh thread to force the thing off the taper. Should have been obvious to one of the meanest intelligence what was going to happen down the road.

I think it would be worth filing off the remains of the raised thread and screwing the thing back onto the armature, and with the mag nuts off (as they are) giving a sharp tap to see if the mag will back off the gear, as you suggest.
I don't think a new nut would do it, as the distance between the lh thread and the rh thread on the mag isn't big enough for you to get the whole of the lh part 'inside' to do its extraction thing (because you'll be up against the rh thread too soon).

The quite good news is that usually the lh thread in the atd survives the failure of the sleeve nut, and the better news is that the nuts are available. Andrew at Priory Mags has them I think, for Beesas and for Triumphs, which have slightly different dimensions.

It really goes to show what a pure c**p design this particular bit is. It's so obviously plain daft. It could have been done using a square shoulder for extraction, but it would have required the head of the bolt to be welded/brazed/otherwise pinned on after making the rest of the thing so it could be fitted, and that would have added ninepence to the cost I suppose. The maker saves a few cents and the owner gets a headache he'd have happily paid to avoid  . . . . it is ever thus!

[Rex]

Be fair Bill, it has taken decades to get to this state!

[groily]

Tis very true Rex - but they don't all take so long!! Maybe this was a good one!

[Jim]

A bit of heat often works wonders.

[BSA_54A10]

Pretty well done to get it out I reckon. As you can see, a really lousy design, relying on the first turn of raised lh thread to force the thing off the taper. Should have been obvious to one of the meanest intelligence what was going to happen down the road.

I think it would be worth filing off the remains of the raised thread and screwing the thing back onto the armature, and with the mag nuts off (as they are) giving a sharp tap to see if the mag will back off the gear, as you suggest.
I don't think a new nut would do it, as the distance between the lh thread and the rh thread on the mag isn't big enough for you to get the whole of the lh part 'inside' to do its extraction thing (because you'll be up against the rh thread too soon).

The quite good news is that usually the lh thread in the atd survives the failure of the sleeve nut, and the better news is that the nuts are available. Andrew at Priory Mags has them I think, for Beesas and for Triumphs, which have slightly different dimensions.

It really goes to show what a pure c**p design this particular bit is. It's so obviously plain daft. It could have been done using a square shoulder for extraction, but it would have required the head of the bolt to be welded/brazed/otherwise pinned on after making the rest of the thing so it could be fitted, and that would have added ninepence to the cost I suppose. The maker saves a few cents and the owner gets a headache he'd have happily paid to avoid  . . . . it is ever thus!

Well kindly inform us what other design is good for 60 years ?
Don't see may 60 year old cars around still running their original magnetos.
Unfortunately nothing can be so well designed or made to prevent ham fisted mechanical morons buggering them.

[groily]

Poor design is poor whether then or now, and there are plenty of examples of both across all eras. Same goes for good design.
Wear and buggering up by people are altogether different. Wear is inevitable, of course, but is accelerated by poor design; ruination by cack-handedness is unfortunate and may or may not be related to design (mostly not).
I stand 100% by my comments on the design of the auto-extract of these ATDs. It is not an engineering design, it is an abomination. The use of the first turn of a left hand thread as a shoulder for extraction from a well-made taper is just plain stupid. It isn't buggering about to undo it the way it was intended to be undone (there being no other way) - they fail because failure was built-in, assured even. Especially annoying as it is perfectly possible to design one of these properly using a proper internal shoulder, capable of lasting as long as you like.
None of us with shedsful of old toys expects to inhabit a wear-free or trouble-free zone - but it is perfectly legit, I reckon, to point out glaring examples of the plain bloody awful. Just as we point out stellar examples of the very good. For the most part, I happen to believe that the things we play with weren't at all bad from either the design or construction point of view - but I shall continue to regard this one particular thing as a classic 'How Not To Make Something', because the fundamental principle is fatally flawed!. Very comfortable agreeing to differ on this particular one!

[Simon59]

Just as an update, I've still not managed to get the drive gear off it's taper. I work for a company that specialises in bearings, and we often have to extract them in various states and conditions from shafts of many designs and age. When I explained this non-work problem to one of my experts, he were amazed that such a design was intended to work after the warranty period was over. He was right, it doesn't, at least in my case.

I've tried most things now, from penetrating oil, to heat, to drifts, hammers and various pullers. I'm keeping restrained in the force that I use in case 65 year old metal succumbs to too much brute force.

The engine comes out of the frame next weekend, when I have another pair of hands, with magneto still attached. I plan to take it all to SRM for a strip and inspection so I hope and expect that they will have seen this particular problem before and will have the right tools and techniques to get the b****r off!

All the best, Simon

[a10 gf]

penetrating oil, to heat, to drifts, hammers and various pullers.

but 'cold' missing from list :0)

Get the mag shaft down to "minus as much as possible", heat the advance center to "max temp without destroying anything". Then a few taps here and there, repeat process until it comes loose.
example https://www.bunnings.co.nz/crc-electrical-freeze-spray-300g-2039_p00648729

[duTch]

  Dunno if it'll hep, but I had a similar but not bike problem the other week; have a read of this- it surprised me
 https://www.a7a10.net/forum/index.php?topic=12775.0

 It may or not work for you...

 On another unrelated note, at work we need to periodically wash stuff with a common garden hose, and a site Ive been at has been storing the tap/hose fittings in the frezzer....yesterday I dug 'em to use, out but  plastic spray nozzle was stuck solid. left it on the deck and by the time I came to use it the sun had warmed it and was like nothing ever happened..

[BSA_54A10]

Just as an update, I've still not managed to get the drive gear off it's taper. I work for a company that specialises in bearings, and we often have to extract them in various states and conditions from shafts of many designs and age. When I explained this non-work problem to one of my experts, he were amazed that such a design was intended to work after the warranty period was over. He was right, it doesn't, at least in my case.

I've tried most things now, from penetrating oil, to heat, to drifts, hammers and various pullers. I'm keeping restrained in the force that I use in case 65 year old metal succumbs to too much brute force.

The engine comes out of the frame next weekend, when I have another pair of hands, with magneto still attached. I plan to take it all to SRM for a strip and inspection so I hope and expect that they will have seen this particular problem before and will have the right tools and techniques to get the b****r off!

All the best, Simon

Wile we all sympathise with your problems, just because some past moron has used a bolt that should ave been binned does not make the whole idea bad.
It is in fact a very good one, designed so Joe Average can pul it off on the side of the road with nothing more than what is in the tool kit.
Now if you want to bitch about the lack of any means of locking the armature while you tighten the said same sleeve nut yo would have my undivided support or even the lack of a locating peg I might line up behind you.
However an A 10 was my very first bike, back in the days of pressed tin ratchet drivers ( remember those ) and I can not remember ever having a problem other than the armature slipping before the taper locked.
we have just finished going over an A 10 that will be loaned out to guests coming for the BSA National.
In this case it came off beautifully however we could not get it to lock.
The culprit was the C washer that had been extruded into a cone shape by a DPO in the past using impact guns to tighten it up.
The A 10 magneto is a lot easier to get on & off than my M20 one with fixed timing gear.