The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: berger on 02.09. 2020 19:18
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has any body got a good spark i can borrow, or has anyone cured their mag of a weak and intermittent spark by fitting one of those new points end condensers? i don't really want to have to swop the mags over if those new thingy condensers work, i can't remember what they are called
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Hi Berger,
The mag has to be stripped to disconnect the old condenser, as far as I know?
Groily will be along to confirm
If you have another mag, I would fit that
20 minute job *smile*
John
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hi john not on mine, swept backs and oil filter and cross over plumbing are in the way of making it a 20 minute job. the price I pay for making it as it is.
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Hmm. Not going to be a pernicious vendor on here of all places Berger.
But - if you have a condenser problem as opposed to summat else, a dodgy coil or whatever, then those pipes and the mag have to come off, so not a 20 minute job I'm afraid
With a K2F/K1F/KVF (or any rotating coil mag with the condenser at the opposite end from the contact breaker) there is the possibility of just cutting a 'link' wire that traverses the bobbin from condenser live side to points. So you don't have to strip the armature itself, which neeeds some tools and/or resourcefulness (I know you have both in truckloads if you can be bothered!) - but in all cases the armature itself has to come out.
Sometimes even with K series mags whose condensers have already been replaced once, the low tension tail wires off the coil can't be got at easily due to their being buried in resin. Delicate is the word in those cases. 99% of the time it can be done, but with great care. If the parts are original, it's a lot easier to disconnect the condenser - but only worth doing if the HT winding remains good. Which has to be a bit of a Question, owing to the possibility of insulation failure or an internal break in the secondary winding. There are some basic tests you can do on that - continuity cold and hot for start, but to be sure of things you need a coil tester of some sort. The Lucas workshop instructions contain info on that which is as good today as it ever was, and explains how.
As to whether the cb end 'EasyCap' capacitors work, then I'd say they do. About 20,000 out there now in 7 different versions, and although I only have 5 of them on my own magneto bikes, I've never replaced one and I don't bother carrying spare ones on my keyring any more. I've probably fitted a thousand or so by now on mags of all sorts from the very dawn of time to Joe Hunt wasted spark units for track use, but I've never really counted! Famous last words of course, as nothing's for ever, but so far so good. The one on my A10 went on before we ever launched the product, so best part of 10 years, and same for one of my AMC twins. But, they had rewound coils, new sliprings etc etc at the same time, so I knew I was starting on a level playing field. Since then I've stuffed them on another AMC twin and 2 Norton engines of my own, also on loads of flywheel magnetos, battery and coil systems, etc, you name it. Rotating coil magnetos are the most delicate jobs to do because of their inherent design . . . but the idea is that if it ever has to be done again, it's a screwdriver and 2 minutes (no swept backs to remove), no mag to take off, and take apart, replace and re-time. We started by saying the things should be regarded as a 'service item' like the condensers that came with sets of points for old cars, but the reality is I haven't changed my own, and don't try to flog the things to anyone else on a 'just because' basis. I don't know what the service life is, and may not live long enough to find out frankly, but absent cack-handed abuse it way exceeeds the 2 years they're warranted for. Fingers Crossed.
BUT, doesn't offer you a super-quick fix I am very sorry to say.
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I've fitted/had them fitted by previous owners on 7 different bikes now, and I have to say I'm impressed with them. The installations have all been done as recommended, namely after having the internal capacitor leads clipped.
I reckon the recent article in RealClassic where some berk just installed the capacitor should have been questioned though as it gave a misleading impression of how the fitting should have been carried out. *eek*
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cheers groily my plan of attack is put my other mag on and then have a look at the naughty one and see what can be done, either by me or the experts. most probably the experts, my limit was re building the competition mag with new bearings etc after the armature was wound at FTW sheffield -- RIP
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Thanks for that Rex. I haven't seen whatever was in Real Classic as I don't see many classic mags out here in the sticks - but if Frank Westworth needs a follow-up ref the fitting, maybe someone will send him one! People do sometimes just stuff 'em on and pray, and I believe in one or two cases there has been an improvement - but it's not the answer and probably won't last with a dodgy condenser still sitting in parallel.
If you're taking the mag off to exchange it Berger, might as well pull the armature out and see the lie of the land . . . ? Might be OK in there, you never know, and the lead-clipping 'Snip' might sort it for next to no ££.
As you say, RIP Mick, really nice guy.
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berger - whatever groily says is the truth! i've fitted 2 and think they are great.
now, i'm also lazy, optimistic and don't always follow advice (when faced with jobs i don't like) and did discover that while most old caps fail by closing the circuit, some (not many) fail by becoming open circuit. think of it as a physical person who has already lost their soul. So if it goes open then adding an easycap (effectively in parallel with the dead one) will help (according to me). So I tried it once. it sort of helped a bit. (but didn't fully solve the problem and yes the mag required the full vasectomy and a rewind after all).
But given you'd be buying a new easycap anyway... could be worth trying before the surgery????
if it doesn't help blame me and have another back and tan.
BTW i'm ticking groily's 'good advice' green button and don't suggest you tick this one ;)
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I had one fitted to the SR mag 2 years ago, works great. I had forgotten how easily a magneto bike can start and how nicely they run when all is well.
I looked at the instructions and decided to take the mag to a clubmate who has been rebuilding Lucas magnetos and dynamos forever. He fitted it and replaced the bearings for a very reasonable fee. I noticed he had a drawer full of new Easycaps, all ready to go. I guess they are a standard fitment for him now. This was good as I had ordered the incorrect type. He had the correct type on hand, so we did an exchange.
I recall he said something similar to what Mike has posted above.
It was " Let's try the Easycap, there's a good chance it will do it.
If not you will need a new armature"
Ever since then bike has been a 1 or 2 kick starter, mostly 1 kick, hot, cold or tepid.
Prior to fitting the Easycap, warm or hot restarting was impossible, hot idle nonexistent.
You could actually feel and hear the running change when enough heat got into the mag.
The engine would develop a flat sound and you daren't allow it to stall or a 1/2 hr roadside cooldown was in order.
Glen
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do you know if your mate just fit the easy cap or isolate the old condenser?
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He removed the old condenser.
Glen
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ok you maggy peeps this is how it is. when I had the comp maggy on and betsy wet sumped to the max it filled the mag and came out of the points cover but the bike ran ok. some time later I took it off and cleaned it up because the armature had been re wound not many weeks before this happened. the mag that has been playing up had got a coating of oil on the magnets but not on the armature insulation or slip ring but a coating on the earth brush. I cleaned it up and as far as my knowledge of sparks goes it's working well on the bench. by the look of things it has a modern condenser fitted and the same insulation as the re wound comp armature so it looks like it was done fairly recent. if the oil affected it why didn't it effect the full up comp one? would a electrical maggy man be able to prove its worth on a bench , I am confused. com *conf2*
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bergs. Probably coincidence, or a possible difference in the specification of a competition maggy to provide reliable sparks under more arduous and testing conditions than a standard built to a price unit. At the end of the day every part of the problem maggy can be checked and tested and a reliable magneto produced. It's a bit like the dentist...the worst part is what it costs, not actually getting it done, that's easy.
Now a consideration of Easycap. Adding this external condenser puts it in parallel with the old condenser. The result of this is to increase the capacitance available across the points. Is this significant? My researches have only provided limited information of how the value for ignition condensers is chosen, and in the old days it was a case of any make or value would work well enough. If a magneto condenser fails when hot, then the Easycap will still still be there in circuit, to run at its normal capacitance. So the extra capacitance is only in use until the magneto warms up and the internal condenser fails. On this basis adding an Easycap without major dismantling has its attraction.
Tin hat on ready for the full explanation of something I've missed and why I am barking up the wrong tree.
Maybe bergs can sell me some car insurance.*
Swarfy
* UK joke.
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Other than an 18mm drive bearing which all K2F's had sometime after the early fifties anyway, and smaller bore screw on pick ups and screw on end earthing caps which many also had, there is no difference between the two.
Some say they had thicker winding's and Lucas would not allow any repairs with solder in the winding process should it snap, unlike non competition ones. All those that have been overhauled will be just the same as any bog standard K2F internally.
The quality control may have been better when they left the factory sixty odd years ago who knows? I think they were just made easier to waterproof should you want to drive through a river.
B.S.A. gave Lucas the remit to build at a price not a quality and it's remarkable they were/are so reliable and long-lasting and durable. Old Joe may not have liked light, but he didn't mind sparks it seems.
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You don't have the new cap in parallel with the original, you must break the connection.
If you leave the old cap in circuit and it fails by short circuit, as I believe happens, the new cap is then rendered useless.
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Trev, That is an interesting thought, if we consider a failure to be a simple open circuit, this is acceptable for capacitors in parallel. Failure due to an internal short certainly is not, and I can see the reason for the so called snip or condensectomy.
So I would reckon if you were prepared to risk your newly purchased Easycap, simply fitting it as is would be worth a quick try.
I found this, and while not strictly within the motorcycle sphere, explains what happens in condenser failure in some cases and offers a possible reason for the unreliable nature of some of our so called Classic Cars when they were new.
http://nonlintec.com/sprite/cap_failure/
bergs can look away now.
Swarfy
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If a condenser has failed open circuit, then stuffing a second one on, whether an EasyCap or even a remote jobbie using brushes etc to make the contacts (highly inefficient!), can work. But most don't fail open circuit, which is the problem, and having a good 'un and a bad 'un in tandem doesn't solve things.
See for some boring detail, and also some pix
http://www.brightsparkmagnetos.com/faqs/FAQs%20about%20magneto%20condensers%20in%20particular/index.htm
As to what is the correct capacitance to do the job, there are reams of stuff out there in tekkie papers etc (much of it way above my pay grade). but as a practical demonstration of different capacitances, these videos may amuse
http://www.brightsparkmagnetos.com/gallery/CB_arcing.htm
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In my experience (employment rather than old cars and bikes) capacitors "fail" due to ageing, and over time become less and less efficient, but even when totally useless for their intended task they still show continuity.
Due to their physical construction, failing either open circuit or short circuit must be most unusual, hence the requirement to remove them from the circuitry in old mags.
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could this brush piccy have been my problem---- discus --- I had a bit more time to study things today and compared 2 brushes. the one on the bottom of photo is from the maggy that up to a few days ago was ok then started miss firing pulling away from junctions and at about 1500 to 2000 revs . once it had got through its spluttering it was ok for a while then sort of gave up after I found the points gap was only 6 thou and opened it up to 12 . after that it was no go. the piccy of the armature tries to show the condensers and are these the modern things they put in? I can just make out FA 271M and swb printed on them. cheers
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Don't think the manky brush will have been the prob berger. They often look like that after a few years and as long as the thing contacts the mag armature, they work. You could easily prove the point with a meter if you felt like it.
If you have a cb with the hole for an auxiliary brush on the rear face, you could always fit one there for future double-sure fail-safe running.
And bear in mind that on mags with steel drive gear components the armature is also earthed, if imperfectly, by that route too. (Not if an ATD with fibre gear is on there though . . .) A lot are also earthed through the bearings due to deformed, broken or knackered insulator cups - but they shouldn't be!
The condenser in the picture is one, or a pair of (can't see too well with ageing eyeballs) Evox Rifa PME271. A common fitment. The coil was probably rewound by APL Magnetos down near Shaftesbury and will almost certainly be very good. The condenser may have failed though, as sh1t happens.
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on the money again groily *yeah* I tried both carbons and the plugs spark was what I would call good in the atmosphere. there are 2 of those flat faced thingy's in there-- condenser's . how are these maggy's tested on a bench to make sure the spark will be good under pressure? or do you use special equipment to make sure things are as they should be? I might have to have it tested before I trust it on an engine which could lead to many £££££'s
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Basically by using an exaggeratedly big spark gap Berger. Lucas said 5.5mm, three point gap and a lot of other stuff. Coil testers and all that . . .
But if you grind the earth electrode off a spare plug and use that, it's better than nothing and offers a gap of getting on for 4mm. You'll get a good 'thwack' as the mag sparks with it. (IIRC - and it's evening here and the BBQ is lit and it's all downhill from now on! - every 0.8mm of gap equals an atmosphere, or something like. So 5.5 mm = 7:1 cr roughly, which was an adequate test back n the day).
At home, a good thing to do is to borrow a hair drier, or use a heat gun, and get the armature / mag hot to the touch - like hot enough to touch still (50°C ish), but not boiling to death - and test for the spark. If you've got a slow-speed drill, turn the mag and see if it makes good sparks when it's hot. Cold, you'd expect to see sparks from about 130rpm and hot from say 160-170 ish (advanced).
With that coil, I don't think you have a problem. I really don't. It is 99% sure to be good.
But I think you need to cut the condenser(s) out and try another. I think if you do you'll get to happy. I really do.
If you can prise out the low tension wire - the double-strand wire - on the side of the armature opposite the boss on the slipring where the HT connects to it, that's the live one - then you should be able to snip it, ensure the two strands are still well-connected, and insulate the exposed end wi' a bit o' heatshrink and instal your easycap on the points in place of the insulator between block and backplate.
I'm pretty confident in this case . . . but as I often say, Famous Last Words - and don't kill me if it all goes pear-shaped and your beer goes down the wrong way!
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Being a curious bu**er I cut open a Lucas mag condenser to see its construction. It was giving a reading of 25, 000 ohms when it should look like an open circuit. It was a folded up sandwich of foil and paper. The problem was moisture must have got in because a lot of the foil had turned green and making a circuit. Easy cap screwed on, end of problem.
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groily / bill have a good bbq and get some *beer*, what you have just done is given me the confidence to go further with this maggy and do the tests you mention. thanks for all your input but don't be surprised if I don't go away too quickly *whistle*
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well chaps I think the journey stops here. I set the points firstly to 12 ish thou and did some tests, then 15 thou ish and repeated.--- I have spun the armature between finger and thumb and got nice big sparks to jump 5mm at least with the thwack groily mentioned. this same spark is continuous with speed and stops sparking after 5ish mm gap. I have done this with HT leads on there own and plugs in caps and got the same result *good3*. does any body think the miss firing it developed could have been the oil coating on the magnets effecting there efficiency ? I know nothing about this except my other mag ran with oil dripping from the points cover-----. thank you all for the input and information on this subject *thanks* …. ps I will not be putting it back on because it takes me half a day to do on my bike ;)
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Just before you call a halt berger, heat the thing up if you haven't. Heat is the enemy in all of this. You certainly seem to have a half decent or better spark cold - but what happens hot is the remaining Big Question.
Oil: A lot of oil on the slipring, or worse still on the points, could well upset the applecart, sure . . . but a bit of slime doesn't kill a magnet, as your other mag proved, so I'd be surprised if that was the cause if the slipring/brushes and points were clean. It's quite amazing how contaminated some mags get, with oil getting in down the plug cables, oil seals falling to bits, you name it. And yet they still work electrically despite everything.
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I will do that tomorrow bill, my brother said it could! be the magnetic density not as good as the other mag that had oil all over it. heat tomorrow and try again, fingers crossed
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I got the maggy hot , as hot as I have felt it on the bike and it cracks off good sparks between finger and thumb with a wide gap of at least 5mm. it also does the same at revs so the gremlin seems to have gone. i am going to add oil to the magnets to simulate how it was and test again, are you excited? i am *roll*
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As excited as a field coil.
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exciter volts have produced the excitement. well the oil film has any way. I set up the maggy with a good dose of oil on the magnets like it was when it was acting the pillock. the result was only half of the spark jump turning with finger and thumb or running faster. also missing some sparks, and this was how it was running on the bike. maybe the oil film reduced the magnetic density acting as a barrier on this mag and the competition mag might have better magnets and overcome this when it was full of oil. I cleaned it all up and the sparks are jumping big gaps!!. They told me they are feeling better. so a new oil seal will be fitted and maggy can have a rest in the bedroom until I need to shout her to do some work *work*
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They told me they are feeling better.
Good way to test your ticker!
Cheers
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tested my ticker twice on 240 since the heart attack, still ticking , I've had AC and DC, ----- what a band *woo*