Author Topic: auto advance mystery  (Read 1069 times)

Offline Swarfcut

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Re: auto advance mystery
« Reply #15 on: 31.10. 2018 09:45 »
 Guten Tag Hans...

    Simple stuff first..check lower magneto mounting bolt does not enter the timing case to catch on the gear.

   If you are using the same auto advance unit as before , then the magneto must be the problem. For some reason the shaft is not sticking out as far as it should.

      First check the ATD , the fibre gear should be a standard 15mm thickness.  The collar on the ATD base should be level with or slightly below the end of the centre taper mounting, pushed towards the fibre gear.. This fixes the gear in relation to the ATD internal taper.

   Without the retaining bolt fitted, the ATD should seat on the magneto shaft taper (conus) and grip with just hand pressure to turn the magneto.  It should not touch the crankcase. My ATD seats on the taper shaft when pushed on 15mm from the end of the thread.  So you need at least 15mm of taper showing.  When fitted, I have about 3mm of shaft showing between the ATD and the magneto oilseal lip, checked with difficulty with the magneto removed.  So you should have at least 18mm of taper shaft from end of the thread to the oilseal lip. From oilseal lip to end of shaft, including thread is  26mm.  Remove the magneto and try this. You should be able to check that the ATD  fits.

   If the gear touches the crankcase  then the magneto is not fitted OK, or the magneto shaft is too short. Maybe the magneto oilseal is too thick or not in its proper place. The bearing may not be fully seated. This would move the magneto armature into the magneto body, (because the bearing is not in the right place) and shorten the available shaft length.

  There should be no need to cut your crankcase. 

   Swarfy

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Re: auto advance mystery
« Reply #16 on: 31.10. 2018 09:57 »

 Interesting and timely topic, as I have mine off at the moment but won't have it back in my possession until tomorrow (work dependant)...so'll measure it up then
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline Happy Hans

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Re: auto advance mystery
« Reply #17 on: 31.10. 2018 11:27 »
Swarfcut I think you are right with the fact that the taper  is not coming far enough out of  the housing.  I recognized when I removed the maggie that the a/r Unit touches the flange of the mag bodie before     getting in contact with the conus.
The thickness of the fibre sprocket is 15 mm.
So what to do? Dismantle the maggie and checking what is wrong inside, or send it back to Lindsley ?


Offline Happy Hans

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Re: auto advance mystery
« Reply #18 on: 31.10. 2018 11:47 »
I tried some pics, hope its possible to see someting.

Offline Swarfcut

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Re: auto advance mystery
« Reply #19 on: 31.10. 2018 12:09 »
 Guten Tag Hans.

    I think you have found your answer. The magneto has not been rebuilt to give the correct length of spindle. You have paid a lot of money for a  magneto which is not fit for purpose as we say in England. You have to decide whether to send it back or fix it yourself.  I would first contact Mr Lindsley, he may advise you what to do, or simply ask you to return it. If the internal parts are are OK, it can only be a simple assembly problem, which you can fix yourself.

  As you have spent a lot, of money I would only try  to fix it yourself if you have no result from Mr Lindsley.  If this is the case, please let the forum know of your experience.

  If you can find the UK websites  for Priory Magnetos or Brightspark Magnetos there is information  there to help you. I would  highly recommend  both of these companies.

   Viel  Gluck

  Swarfy.

Offline Happy Hans

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Re: auto advance mystery
« Reply #20 on: 31.10. 2018 12:15 »
Swarfcut and all the others thank you once  again. I love this forum
Let you know the results after connecting Mr. Lindsley

Online groily

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Re: auto advance mystery
« Reply #21 on: 31.10. 2018 17:13 »
Just went and measured a couple of customer K2Fs to compare with your measurements Hans.

From the circular raised register on the drive end flange to the end of the threaded section (when all threads are there as yours are) is typically 7/8ths of an inch - 22mm in metric. The thickness (depth) of the collar on the inboard side of all the 4 Beesa-spec atd units I have here is 5/16ths from the rear flange of the centre section, give or take a gnat's cock as we say - or 8mm.

Your pic seems to show 19mm sticking through from the register - which is 1/8th or 3mm short and more than enough to cause the problem.

As to 'why', it is hard to say. I rather doubt Dave Lindsley would have put bits in the wrong places on the inside, but there must be some problem with the internal fit - or something unimaginably horrible has happened to the armature in the past resulting in a loss of length which couldn't be rectified without replacing the whole armature.

It is just possible the oil seal isn't sitting properly in its recess behind the drive end bearing race, or that the race somehow didn't go fully home. If the latter, you'd notice because the oil seal would be a loose fit. It is also possible that there is shimming on the drive end (behind the bearing's inner race) which would shorten the bit that sticks though to the atd, but I can't think why and 3mm is inconceivable.

It might be worth taking an HT pick-up off and seeing if the brushes are dead-centre on the slipring at the other end though, which they should be. If things aren't aligned correctly there, that would tell you something.

Although your mag might (probably) take a simple sprocket or gear, with fixed camring mags designed for atd use, I think most of us do a trial fit with a known good ATD after assembly to be sure one will go on and stay on. I have a spare timing side crankcase lying about which I use just for this purpose. It's not totally foolproof and the problem of folk finding their own atd won't go on isn't unheard of, to be honest - Beezermac at Priory Mags has a brilliant bit of text on his site about what to worry about and what NOT to worry about with the things, which I quote frequently to people who are concerned. But a desperately worn male or female taper is a problem you can't get round in a hurry.

If you are going to have a look yourself, bear in mind that it could affect your guarantee . . . but, that said, it would only take 15 mins to have a look if you wanted:
*contact breaker off
*pick-ups off
* earth brush (next to the drive end flange on top) off
* SAFETY spark screws out - diagonally opposite, 2 of, at HT pick-up end
* cb end housing off - just a few screws
Then you can pull the armature out. The magnetism won't run out all over the floor . . . so no need for keepers on these ones.

Then, you can look at the inside.
First, check the cb end bearing outer race is flush with the housing it sits in. It should be near as dammit. It can't really have sunk too far in to cause the drive end to be 'short' - but funny things do happen.
Then, look down the body at the drive end. You should see the outer bearing race flush or near-as with the alloy it sits in. If it's well proud, there's something wrong. Behind the race is an insulating washer to prevent return HT current passing through the bearing, and the oil seal. The oil seal should be dead central and not at all loose. If it's skew, there's a prob as it will have stolen valuable space in getting trapped out of line. If it's loose, then the bearing race, or the insulator, or something isn't fitted correctly. Sometimes, the housing will have been messed up in the past if (for example) someone has  tried to 'pop' round the race to retain it better, or if it has at some point spun in the housing. But it probably hasn't.

If all is solid but the race is sitting proud, then you need to investigate further, which can be a tricky one depending on how well fixed the bearing race is. Sometimes heat and a bit of pressure on the oil seal will get it out without hassle. Other times it won't - and excess force will destroy the seal for sure. In that case, either a one-off tool - we use the thing shown here - www.brightsparkmagnetos.com/workshop/BitsAndBobs/index.htm which is quite simple to make if you felt adventurous. Or, a bent instrument with a sharp edge to lever at the race to see if it will start to budge (fiddly though as hard to get in there). Worst case, folk have been known to drill 2 tiny holes from the outside to bear on the race and knock it out with a hardened pin  . . . at your own risk! Heat, though, in all cases  . . . a good dunking in boiling water can be good, or a heat gun applied carefully. Blow lamps  . . .  hmm! Last resort and only if you have a new seal available!

There should be nothing behind the race except the insulating paper washer and the seal, and the race should go fully home as stated. The race should have a depth of 9mm if it's an 18mm id bearing (post about 1951) or 8mm if it's a 15mm bearing (early K series only). It's highly unlikely there'll be anything funny about the bearing itself but if there are any shims behind it packing it out, then questions questions  . . .  Shimming should normally only be done  between the slipring outer face and the inner race of the bearing at that end, with possibly some large shims between mag body and cb end housing.  Typically on a K2F, there'd be approx 0.5mm next to the slipring. Sometimes there's nothing, sometimes there's a bit more - but the shims come in all thicknesses and it is usually possible to get the end float controlled to a 1/1000th of an inch without trouble.

The worst thing would be if there is a weirdo aspect to the armature itself. The drive end steel shaft should be absolutely solid in its brass end piece, and no signs of damage or repairs for choice. The coil in there will be the one that was fitted before you had it rewound, and ditto the other brass end piece - they live together, and are always best kept together unless there has been a mechanical disaster which has forced a mix 'n match approach.

Mechanical disasters happen when the drive end axle goes sloppy. When the coil has been so messed up it can't be rewound (rare but it happens). When the earth brush track on the drive end has worn such a groove or dimple in the brass it can't be trued without actually going through the brass (that happens too). When a mag has seized due to insulation leakage gluing it solid and things have got busted or bent. In all such instances, mix 'n match may be necessary, or a complete replacement armature in better condition needs sourcing. That is usually possible, but harder with the early 15mm shafts than the later 18s. In all such cases, it makes life harder for the repairer, and the result may not be quite as good as when the thing left the factory. But there are always answer  . . . just a Q of figuring out where your 3mm got to.
 
(If only all problems of length were just 3mm ones - Audible Sigh! - but that would be for the 'ealth and 'apenis part of the forum!)
Bill

Offline Happy Hans

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Re: auto advance mystery
« Reply #22 on: 31.10. 2018 21:11 »
Bill, a lot of helpfull details, thanks for your effort.
At first I get in touch with Mr. Lindsley, I payed quite a lot and I think there should not be any problem. The circumstance which I do not like is the permanent waiting of parts which I have to send back because of the faulty quality. Always two steps forward and one back.
If there occure further problems with the part, I will use your instructions and fix it by myself.



Offline morris

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Re: auto advance mystery
« Reply #23 on: 31.10. 2018 21:15 »
Measured a magneto I have laying around. Shaft sticks out by 22mm
Then tried a known good combination and this is the outcome;
'58 BSA A 10 SA
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Re: auto advance mystery
« Reply #24 on: 01.11. 2018 09:45 »
 Nice War and piece (sic) epic groily *eek*- serious good info...

  FWIW, I retrieved mine from the magneto hospital today, and the taper and thread are much the same as the new swappie acquisition ~23.9 mm o/a, more or less equal thread and taper..(~11.85mm/~11.8mm)... looking at the pics, it seems there's not much between the mag bodies and ATD , of both morris and Hans.....whereas I have  gaps ranging from ~0.035" to ~0.050" (3/4mm - 1,1/4mm)....depending which spare gear I try...
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online Greybeard

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Re: auto advance mystery
« Reply #25 on: 01.11. 2018 10:10 »
Groily, I have so much respect for your posts! May I suggest that you submit some articles to the BSAOC magazine; The Star. I'm sure many BSA owners would enjoy sharing your knowledge.

Offline Happy Hans

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Re: auto advance mystery
« Reply #26 on: 06.11. 2018 18:07 »
Hello again,
meanwhile I had contact with Mr. Lindsley. He said that it couldn't be his work which causes the problem, but I can when i wish send it back and he will take it on the schedule. That means for me that he is not interested in doing any warranty work, and if he have a look it will cost me something, also I will have to wait if he is ready.
Therefore I decided to have a look by myself and I put the magneto apart. I noticed no obvious fault, checked the bearing seating at the driveside. I measured the distance of the flange of the inner race of the drive side bearing to the A/R Unit (see pic). Eventually there is someone who can verify if the distance is correct or the A/R Unit is too deep onto the taper. In this case it is wether the Unit or the armature which is faulty and I'will measure some more if possible after instruction how to do.

Offline Happy Hans

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Re: auto advance mystery
« Reply #27 on: 06.11. 2018 18:10 »
I want to replenish that its measured when the Unit grabed the conus.

Offline morris

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Re: auto advance mystery
« Reply #28 on: 06.11. 2018 19:31 »
Hi Hans, this is a real head scratcher...
Was that ATD fitted on that magneto originally? A difference of virtually nothing on a taper diameter can make a huge difference in distance. Ideally you should get another ATD to compare. Anyway I do have the impression that the unit sits to far on the shaft. For me it’s either the taper from the shaft or the taper from the ATD which is incorrect
BTW, don’t trust anyone who says it can’t be his fault. *angry*
Any decent person would at least have a second look free of charge certainly if you would offer to pay the sending costs.
Did you ask him to rewind the coil? If so, maybe he took a “pre-refurbished” other shaft to replace your original.  *dunno*
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Offline kiwipom

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Re: auto advance mystery
« Reply #29 on: 06.11. 2018 19:56 »
hi guys, Happy Hans ( maybe he took a “pre-refurbished” other shaft to replace your original ) that would be my guess as nothing should have changed apart from the new work i dont think Mr. Lindsay has done himself any flavors with anyone who has read these posts,  good luck, cheers
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