Hi,
So there was me thinking buying a 1924 BSA roundtank would be a great idea, how hard can it be to get it going again. I've watched all the usual bike programmes where they clean the plug and points and tickle the carb and off they go. Hmmm some chance.
So being very new to the vintage world I've started to try to recommission my new(very old) round tank. First thing was no spark. New spark plug, still no spark. I've cleaned the points and checked the gap and they seem fine. They rotate as they should and open and close. The cam ring turns when the Advance/retard lever is used as it should. I have continuity through the HT lead. So I decided to get the Magneto off to either try and open it up to check inside, not that I'm entirely sure what I should be looking at, or to take it somewhere to get it refurbished. I've managed to detached the Ad/retard cable and HT lead. I've got the front case off and the points out. I've removed the casing on the offside of the motor and am now stuck as to how to remove the cog which seems to be on the shaft through the magneto. There's a nut but I can't see how you can hold the cog/magnerto shaft whilst trying to undo the nut. From what I've discovered the cog is held on a tapered shaft which I understand I'll need a puller to remove the cog but can't work out how to remove the nut or if I even need to. Apologies for the long winded question but figured it best I explained where I'm at and what I've managed so far.
Any advice would be great.
Thanks Andy
Before you go any further I would put the mag back together, you can do a lot of damage. You'll needed a puller to get that ger off once the nut is undone but do that and you loose the timing so I would be putting the mag back together and doing some more cleaning of the points and brushes.
You got the mag armature on one bearing and there are some easily damaged parts so stop now until you have read the manual for the mag. I've seen too many with broken slip rings due to being dismantled in the wrong order.
Hi,
Thanks for the advice. Any idea where I might find this manual you both mention. I'm new to the club and new to the world of vintage and this age of bikes. As for putting the front case etc back on the magneto I'm still unsure how that helps me in undoing the nut that appears to hold the cog in place. I understand the need for a puller to remove the cog/gear correctly but as soon as I try turning the nut the spindle or axle for a better term that runs through the magneto just turns and will turn the points etc if back in place. Also the brushes you mention, I've yet to get that far into the magneto. The points are definitely clean and the picture on the right is as far as I've got dismantling the mag from the points side as two of the screws are completely siezed hence why I need the mag off to take it to an engineer to get them removed with no damage.
Thanks again Andy
So forgive my stupidity, as I say I'm am very new to this age of bike and am learning as I go. I've done some more googling and it appears I've seen the brushes you mention. I just didn't realise the brushes looked like that, I was looking for an actual "brush" I did say I'm new to this 🤣
I've seen two "brushes" one attached to the HT lead and one somewhere else which I can't remember off the top of my head. I did give both of those a clean, as for the timing sadly I think I've already messed that up by trying to undo the gear and turned it to a different position it was in. That at present is the least of my problems.
Andy
You really should try to keep the armature back in the magneto body as it acts as a keeper for the magnets in the body.
The National Motorcycle museum have Instruction manuals for this Magneto.
If you search You Tube for "Lister A 1924 vintage engine ML magneto strip down", you will find a helpful video.
To remove the drive pinion (cog), you need to refit the idler pinion, then you can jam something between the teeth to lock the pinion. Ideally, a very small pinion can be dropped between the teeth (if you can find one). I use one taken from an old Black and Decker jig saw. But be careful if using a screwdriver as you may chip a tooth. Use a big one. You could also make a jam from round bar with a diamond shaped end, to fit snugly between the teeth.
If you do decide to remove the armature, (the spindle or axle you refer to) be sure to remove the earth brush first, and as suggested use keepers.
If you search the Brightsparks website, you will see how to check the secondary windings using a multimeter.
If you have removed the armature you can also see if the armature is producing a spark by connecting a battery. With the points base plate removed, wrap a piece of copper wire around the slip ring (the bobbin the HT brush runs on), and then bend it so it is about 3/16" away from the body of the armature, connect one side of a 1.5V battery to the body and jab the other end on the points centre screw. It should produce a spark each time you jab it.
Let us know how you get on.
Thanks so much for the advice, as I say I'm very new to this age of machine and already feel like I'm fumbling around in the dark. I'm already learning things like what the actual armature is that I keep reading about. Lots more googling for me before I attempt any more. The armature is still in the magneto body, if I'm correct I don't think I can get that out without having first removed the cog from the other end of the armature. Again thanks so much for the constructive advice, much better than the RTFM response I first received which now seems to have been deleted by whomever posted it.
I will do so more research and let you know how I get on.
Thanks
Brightspark magnetos have up loaded some of the manuals, I have put the links below.
A magneto is a piece of precision equipment and you should think of it like an antique clock, not a bit of old motorcycle. Take it apart the wrong way and you can do a lot of damage.
https://library.brightsparkmagnetos.com/library/ML%20Magnetos/index.htm
A magneto will reliably produce decent correctly timed sparks for over 100 years of use, there's no other ignition technology that comes close. They need periodic oiling and cleaning, but not much more. Most of the damage I have seen is due to them being dismantled wrongly or overheated.
Thanks for the link, I've found out it's an ML MCK1 apparently from what I can see on the side of it. I'll take a look at the YouTube previously mentioned and the link you've provided, fortunately I'm up at the national motorcycle museum next week so hopefully I can get a manual then.
Thanks again.
I took a look at the pictures and it looks like it has a safety screw on the underside. This means the armature MUST stay in until that is removed. There will be an earth brush too but I'm not familiar with ML mags.
Thanks for all the advice. I'll try and get the manual from the museum next week and see if I can speak to any of the restorers there.
You are quite correct in saying that the cog has to be removed before you can withdraw the armature. Use a puller and do not try to lever it off or the alloy crankcase extension will break off. Likewise if you use a screwdriver between the teeth and the extension to trap the pinion (cog!) whilst undoing the nut.
I must say that dealing with the intricacies of a magneto as your first foray into vintage motorcycles is interesting, but you have to start somewhere, and you will learn a great deal. As mentioned, just try not to break anything.
Once the armature is out, it's easy to check the secondary resistance (the most likely problem, together with a faulty condenser.) Just connect a multimeter on Resistance, to the brass in the slip ring and the end of the armature shaft. It should read about 4,000 to 7,000 ohms. It not, it is almost certainly Fubar, and I would recommend sending it to Armoto for attention.
Thanks again for all the advice, and yes tackling the magneto of a 102 year old bike wasn't exactly part of my grand plan when I bought her but hey you live and learn and I'm definitely learning. I took a look at the you tube video you recommended and it helped alot in recognising the parts and putting correct names to them. I do need to get my eyes on a manual though, the video suggested the earth brush was a screw on the top case opposite side to the HT lead but mine doesn't have one, the only screw on the top seems to prevent the cam ring turning further than it should in either direction. I'll be back in the garage in the morning so will investigate more.
Again thanks for all your help so far. I'm sure this won't be my last post pleading for help 😬
After all I've got to put it all back together at some point and get the timing right.....
One quick question, is it possible to check the secondary resistance without removing the armature, possibly by feeding a copper wire with insulation around the wire so it doesnt connect with the mag body through the HT lead opening down on to the slip ring and then connect the multi meter, one to that wire and the other to the armature shaft? I'm just thinking if that test proves the secondary resistance is fine then I might not need to remove the cog/ armature and prevent any damage. Which I'm guessing, probably wrongly, would suggest the slip ring needs a good clean and another good clean of any brushes and points. Ever the optimist.
I think the short answer is yes. The problem with removing the armature is that there almost certainly is a steel safety screw, this is about 3/4" long and sits in the middle of the (fragile) slip ring. It stops the armature being removed and should anyone try it hits the slip ring and breaks it. It looks like the screw on the ML is removed from underneath so you can't get to it with the mag on the engine. Its job is to earth a HT spark if there's no HT connection to stop it sparking inside the windings.
I would reassemble the mag end cover with the existing shims and check it spins freely with no end float. Strip and clean all the parts of the points and clean the HT brush and spring. You can put a cloth in the HT hole and turn the mag over to clean it. Do the same for the earth brush and slip ring (where ever they are on your mag).
There's a chance that after this is will spark. Mags are very sensitive to dirty points and corrosion where the points bolt to the holder.
If you do a search there are some examples of simple electrical tests, I'm sure one is slip ring to points holder.
Make sure you have the rotation correct, then you can spin it up with a cordless drill and a short bit of rubber hose on the nut.
Thanks gents for all the advice, I've definitely learnt lots from this post. I've identified the HT brush, the only other brush I have found is on the reverse of the brass mount of the points, I'm assuming that earth's against the points cover which in turn earth's to the main mag body. Other than those two I haven't seen any other brushes or found any other screws that have anything that resembles a brush attached to them. I think I'm going to try the secondary resistance test followed by a good clean of all parts before putting the points and cover back on, then I'll see where I'm at. Then just need to get the timing sorted as I replace the cogs and cover on the offside of the engine. Fingers crossed 🤞
I think I may have confused you regarding my 2 separate suggestions of 1. Checking the resistance and 2. Testing for a spark using a battery.
When checking the resistance, there is no need to wrap a piece of wire around the slip ring, just touch one lead of the ohmeter to the brass on the slip ring and the other to the end of the armature. I suppose you could place the probe through the pickup hole?
I have not seen a magneto without an earth brush, (but neither have I seen an ML magneto) which would run on the brass at the opposite end of the slip ring. This would be in addition to the brush you have found on the points base plate. However, even if there is a hidden earth brush, and you remove the armature, the worst you will do is break the carbon brush. (Easily replaceable.)
Normally, the resistance would be checked with the armature removed from the body, to eliminate any possible false readings.
You really must bite the bullet and remove the pinion. You may be lucky with giving it all a good clean and repack the bearings, but this is most unlikely, and to do this you will have to remove the armature anyway. As you go through the machine, you will find that you have to use a puller on various things, so you might as well start now.
My understanding regarding spark safety gaps is that they are only used on multi cylinder machines, since if the HT becomes disconnected on a single cylinder machine, the engine will stop and so the magneto will not produce a spark.
On a twin, if one lead becomes disconnected, the engine will continue to run and the spark will have nowhere to go, so it will try to spark inside the windings, hence the safety gap. But what do I know.....
I agree the earth brush and safety screws are confusing. My K2F twin mag has two safety screws but my K1F single (on a Matchless) also has a safety screw and unlike the the K2F where you can see them, its underneath. There is a screw underneath on the ML which could be the earth or it could be the safety, either way it looks like it can only be removed with the mag on the bench.
The safest thing it to put the end cover back before taking the gear off so the armature can't end up resting on the screw or brush.
Thanks again, I've been in the garage this morning. Thought I'd try cleaning the slip ring through the HT lead opening. Used a clean cloth soaked in petrol and held it gently in place with a screw driver. Fear not the cloth was doubled over and very minimal pressure was used. It actually seemed to remove a fair amount of what must be carbon build up. It was difficult to see properly but when I'd finished it certainly appeared cleaner. I tried the secondary resistance test, managed to get one probe through to the slip ring, the other held on various positions on the armature spline where the points fit, got absolutely no reading. However as pointed out that isn't definitive with the armature in situ. So I decided to try my luck, cleaned the brush on the end of the HT lead and the one which protrudes from the rear of the what I think is the points base plate, cleaned the contact point of the points case where that brush will or should contact. Greased the bearing ring, reattached the points case and then the points back plate. Attached HT lead, brand new spark plug, re checked the points gap and went for it eith a drill in slow speed attached to the nut on the cog. The armature spins freely and easily, doesn't seem to wobble and the points open and close just no bloody spark still 🤪 told you I was the eternal optimist. I'm going to the motorcycle museum next week to get the correct manual and see if there are any of the restorers around to show pictures to in the hope they can point out stuff. I really appreciate all the advice you have both given. It's definitely helped me in learning parts names and things not to do and things to try. I'll keep you updated on how I get on. The only other thing I have thought is to try new brushes, not sure if you guys know a good place to get some from. They are on ebay but who knows where they've come from or quality.
Thanks again.
Well you've made a lot of progress even if its not fixed yet. Mags can be very frustrating, I spent hours building up one from all my best parts and had persistent misfiring and poor starting. Out of frustration I put all the left over parts together to make a 2nd mag and its been a gem. I then wasted hours substituting one part for another to work out why one worked and one did not and I never worked it out.
Thank you, Rob for putting me right on safety gap screws.
Andy, I would purchase brushes from Brightsparks. I'm sure they're good quality.
I had an armature rewound a year or two ago, by one of the best rewinders in the UK. It worked fine for a while, and then became difficult to start. The spark seemed to come and go on a Spark Gap Tester. It was OK on full advance, but poor on full retard...(you may want to try for a spark on full advance.) Everything looked OK, secondary resistance was good, so I sent the whole mag away to be remagnetised....just in case. No difference. Just like you, I spent weeks of checking, I finally renewed the pickup brush with one of unknown origin, even though the old one looked OK. Well, it made a difference, but not for long and I was forever having to clean it. Then I bought a new brush from Brightsparks, and, fingers crossed, it seems OK now. We shall see.
From what you have said, it does look as though the secondary windings have a break in them.
I wonder if Rob can add to my encouragement to remove the pinion? Otherwise, you're just going around in circles.
Thanks, from what you guys have said about problems with magnetos it's reassuring that it's not just me. I think I'm going to find something to help hold the pinion safely while I try to loosen the nut then get a puller to remove it, once off the whole mag is going for refurbishment. I haven't decided where yet, I've seen various places recommended on other forums. There's several screws with heads that have nearly been stripped and two that are gone completely so it wouldn't do it any harm to have a full refurbed looking to the future.
Just to further my knowledge, if as I say I tried to spin the mag with the drill directly on the nut holding the pinion to the armature but didn't have the advance/retard wire attached and I think it's a tight wire advance, would that make any difference to getting a spark? And I'm right in thinking even if the mag was completely free from the bike so long as I held the spark plug against the engine block I'd still get a spark if all was working fine? I'm just confirming I don't need to put the other three pinions and case all back together and get the engine correctly timed just to achieve a spark?
Andy
if the mag is "completely free" from the bike then the plug won't spark on the engine block no matter how good the mag is.
Place the plug against the mag body if you want to check the spark.
They are set to spark best at full advance so you do need the cable to pull the cam if its tight wire advance.
Okay thanks, again just for my future knowledge. If the mag isn't on the bike and thus the timing of the engine/piston has no bearing on when it sparks for best combustion surely it wouldn't matter if advanced or retarded if I'm just trying to create a spark from the magneto? I bow to you guys far better knowledge. Am I confusing the whole point of advancing or retarding when the spark occurs?
For technical reasons of getting the best spark you need to put the mag at full advance to get the best spark for testing when it's on or off the bike.
All to do with the intricacies of peak flux density etc.
Okay, that just proves how little I know and how I wish I'd listened more in physics o level all those years ago. 🤣
There are 2 separate reasons for advancing the ignition timing on a magneto. The first is that it allows the engine to develop more power which means you go faster. The second is that, as has been said, the magneto produces a bigger spark when advanced, but probably won't make any noticeable difference to power output.
You might want to invest in a Spark Gap tester. Otherwise, forget the spark plug, (it may be faulty) and just securely hold the end of the HT lead about 3/16" to 1/4" from the body of the magneto with it in the fully advanced position. It should produce a spark.
You do not need to put the other 3 pinions back together and time the engine just to produce a spark. The magneto is completely self contained.
Do remember to spin the magneto in the correct direction of rotation, and also that if the magneto spins, say, clockwise viewed from the drive end, it will spin anti clockwise when viewed from the points end.
The face cam will turn in the opposite direction of rotation of the points to advance it.
You may find a copy of "The Vintage Motorcyclists Workshop" by Radco useful.
Thanks, I'm slowing getting to understand all the wizardy that happens in a magneto. The spark plug I'm relying is brand new and have tried several other brand new ones and no joy so I'm guessing there's something more than that. I'll try the HT lead near to the housing just for the hell of it. I think I just need to put my big boy pants on and get the pinion off then I can send it off for a full refurb.
Not today though, the sun is out and one of my other rides is screaming at me to take her out. Off to have some fun...
Trying not relying