The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: a101960 on 19.10. 2020 14:25
-
Anyone know where I can get my ATD fixed? It needs a new gear. I found a couple of teeth were chipped when I removed it today.
-
Perhaps Priory Magnetos or Brightspark Magetos could be of help ?
S
-
The fibre gear is available with the rivets and can be fitted at home. The gear is also available in aluminium. The fibre gear will wear out eventually, but they have a short life if the magneto bearings have any movement in them.
Priory Magnetos is the place to go in the UK.
-
Priory does'nt appear to be trading at the moment. Notice on website home page says due to work load no more work can be undertaken.
-
You can buy new old stock if you want to spend $500!
http://www.klempfsbritishparts.com/auto-advance--mag--bsaarie-0
Some ebay ATD going for over £100.
-
Worth giving Priory a call. Although the site says no more work can be taken on, I'm sure straightforward sales of bits would be welcome.
The technical pages show how to do it, and there are also YouTube viddys of fellas replacing the fibre gear.
Nothing from the Prince of Darkness was too complicated for a backyard fix. OK, getting perfection took a bit more skill, but the average Joe could get mobile again.
Swarfy.
-
Dave Lindsley Magnetos list them new at £225, part no DL422.
Priory offer recon jobs at £120 (when available I guess). And have the best explanatory text & pix you'll find.
Gears in fibre or alloy, rivets (& also springs) are available, as mentioned already.
The problem with these things is that all the little parts wear, and are a fiddle to replace/ make, so a lot of folk are reluctant to play with them - and don't have them for sale 2nd hand because there are too many areas which can cause 'disappointment' to a purchaser with a critical eye.
Be it the central pillar (worn, rusty even), the pins for the weights (oval and undersize, no longer vertical quite often), the weights themselves (oval holes), the plate the weights slide across (scored to the point the ATD doesn't operate smoothly), a self-extract that won't, etc. That's without thinking about the gear itself. It's a labour of love to get a tired one back to a truly saleable condition and original usable parts for cannibalising aren't easy to come by.
On the basis of 'better the devil you know' (if it works OK) it's probably worth just getting a new gear and rivets and going the DIY route.
-
For those folks buying on eBay, from experience here is what it said, and what it really meant.
"Moves feely as it should"........Rattles when you shake it.
Slight wear to teeth................Fibre gear Knackered.
The picture is the description.......Damage is out of view in the photo.
Barn find condition...........Seized solid.
As Mr G says, for such a simple assembly the pitfalls are many, but actually when under power the various bits are locked together and you won't be too bothered as long as the thing moves and maggy goes to full advance.
Get the bits, have a go, and if it all goes horribly wrong then spend as required. Well seized ones loosen up with the heat gun, (shield the fibre gear otherwise oil soaked and relatively soft it will char) and are a better bet than a rattler. At least the moving bits are a bit close, that's why they seized. The rattlers are the well worn examples, but can be improved by pressing the collar on a little bit more.
The self extracting feature is a bit of a Unicorn. I've heard of it, but never seen one that worked.
Swarfy.
-
I have only played with a auto advance once many years ago and it didn't have the washer and C clip so what are these parts all about and how do you fit the clip when the nut is tight or do you fit it before tightening, I can't see a reason for these bits because i'm still on a thick week *conf2*, ps it seems good not like the rattle non returning unit I stupidly bought on evil bay *bash*
-
Hi Berger,
The C washer and its dished seating are needed otherwise the bolt will bottom out on the threads before
the ATD is tight on the taper
I do not know why they made it like that though
John
-
I C so they go on together and tighty upy, would love to know why it is this set up though. anyone??
-
Designed by the same bloke who thought it was OK to use the first turn of a left-hand thread to take the load on self-extraction Bergs.
Swarfy says somewhere that an ATD that self extracts correctly is a 'unicorn'. Others here have had better experiences and defend the design. I am in permanent attack mode on this, born of many battles.
All I can say is that I love the principle of the ATD but strongly dislike the execution by Messrs Lucas. The dished and horseshoe washers are the least of it - I have no idea why that particular combo was decided upon.
Getting one apart when the left-hand thread completely refuses to engage to allow removal of the central hollow bolt can waste half a morning easily sometimes, the other half being absorbed by making a new centre bolt with a decent thread. Yuk.
-
The chosen design of the centre bolt dictates a "C" washer, why the design of the bolt was chosen I do not know.
Photo shows the rare occasion when the centre bolt comes out.
-
i think i have it *eek* bolt out of unit, washer on bolt recess to unit ,C washer slipped on -tighten up, and hope i get it timed first attempt because it will strip the left hand thread *pull hair out* the only one i ever played with on a bike was missing these parts
-
Hi
The bolt has two functions, to hold the ATD unit in place but also a function an extractor. The external thread fits into the thread of the ATU unit when you remove the C-disc. But often the thread in the ATD unit is broken.
I hope it helps
Regards Svend
-
The left hand thread may be reluctant to engage, but there is no doubt it won't just pull out and come through the unit, hence Mr G's frustration. The thread is supposed to engage with the ATD centre, and as the bolt moves up the armature thread, pushes the ATD from the armature taper.
A drilled and tapped hole into the end of the troublesome bolt would allow a smaller setscrew to push against the armature shaft and either draw off the ATD, if you're lucky, or remove the offending bolt ready for plan B if you're not. In practice the troublesome bolt needs to be clear of the armature thread, which may not always be the case.
Not saying this is ideal, and armatures do not like big hammers, but it could be a possible solution where the extracting threads slip or do not engage as designed, or lockup with some interference between the bolt left hand thread and the ATD centre left hand thread.
Priory Magnetos have a simple illustration of what goes where and how this infernal so called self extracting device is supposed to work. Look in the ATD Section.
Swarfy.
-
hello swarfy I thought this was the ATD thread it says so ;) also the left hand thread engages with or without the C washer, what a piece of magic this thing is. as I have said when I come to use it I hope things go right first time I have one in the shed that the nut doesn't want to come out of. it doesn't matter because it rattles like a snake and needs lots of *work*