The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Devlin on 19.04. 2023 14:16
-
Clutch etc all done time to try and get a spark, new plugs, leads, pick ups maybe, I will be making up a new wiring loom the cables are as brittle as a tattie crisp, So do I need a battery or will the mag produce without a power supply if there is anything I should need to know in the way foilbles of the mag has
Devlin
-
The battery on an A10 running with magneto is only required to back up the lights. Magneto,s require regular maintenance, start by cleaning the slip ring, then clean up the points, check the pickup up brushes and the earth brush. Plenty of information within this forum literature library.
-
I think I will remove the magneto to work on it and maybe send it off for a professional overhaul so is the drive quil splined, keyed or tapered if tapered is there timimg marks I should look for when reassembling
Devlin
-
The drive spindle is tapered, with geared pinion locked inplace with a nut, you will have to retime the ignition after magneto removal, you will need an extractor to get the drive pinion off.
The biggest challenge is retiming the ignition, as you need to prevent the magneto spindle rotating whilst tightening the drive pinion nut
A lot depends on the tapers matching up, some times they need lapping to achieve a decent hold.
-
Hi Devlin,
does the bike have manual or auto timing device ? if its auto then the atd unit should self extract as the nut is undone..
Have a go before you pull everything apart to see if cleaning the points and slipring wil provide sparks
John
-
Quick and easy guide to ignition timing on this page.....
https://sites.google.com/site/cheshirebsa/tech-tips
-
I removed the points complete with the carrier and cleaned everything but I feel that an insulation top hat washer is missing from the bottom of pivot post as the points assembly semm to move from side to side as if not seated correctly, re
Made the HT leads at both ends ,where is the slip ring mentioned I get no spark from the bared ends of the HT and I see no sparking at the points, admittedly I have no experience of magnetos
Devlin
-
You need a pic that speaks a thousand words . . .
See page 5 for a K2F.
-
Thanks, the mag I have is on page 6 so its an auto A/R, but I am going to have to get a set of Whitworh spanners and 3/8 drive sockets as I can get into bugger all without them and it looks like I need the oil tank out of the way also
Dev
-
You need the right spanners, yup. A few open-enders and rings, half a dozen 3/8 drive sockets, and you should be fine for starters. Any allen screws will be imperial too, and if you start playing with electrical bits, they are BA. All available, and I'd guess 50 or 60 imperial squid would arm you adequately for the moment.
But the oil tank stays put, don't go there unless there's another reason.
To get the mag off, it's timing cover off, ATD auto-extracted if it will, two nuts off adjacent the mag flange on top, one long one that you undo from the primary side, and off it comes.
What you do then depends on your motivation and being sure you know what you're doing - best option if you're sure it doesn't work but not sure what to do next is to talk to Cheeserbeezer on here. Same with the dynamo and / or regulator.
-
Update I have removed stripped and cleaned everything.the auto A/R seems in good nick as do the pickups although the earth brush seems short at about a 1/4 inch and I am not convinced that the points parts are all there I made up a insulation washer for the pivot post and I now have making and breaking continuity I still.have no spark from the ht leads as I don't have the gear needed to test the windings is there a simple test I can do with a continuity meter I can also do a insulation resistance test up to 1000 v DC if I know where the probes or clips would go
Dev
-
For the basics, across the points (with them open) just a few ohms, from the pickup to the body a few thousand of ohms. You need at least 500v to test insulation. Should be possible to get a good spark just by flicking the cog.
-
Several points there Dev.
The earth brush is quite short compared to the HT ones - too long and it will be coil-bound against the armature.
The insulator on the pivot post you mention may just be the little pimple that helps retain the blade that goes on top of the thing. Not an insulator, the opening point is earthed anyway.
To check if the bits are all there, see the exploded view attached. Ignore the circuit board - that's a 'me' thing - where it is shown there should be a simple insulator in mica or similar, between the fixed (live) point brass mounting block and the backplate. As well as a fibre top hat insulator that goes through the backplate and through which the centre screw (also live) passes. Both need to be good. As does the third fibre insulator that isolates the small retaining screw for the fixed point block - and the blade spring of the opening point mustn't touch the brass.
Making and breaking continuity with the points assembled on the mag is sometimes hard to see. If the cb is off, you'll see it, but if mounted and the centre screw is in, you won't see much difference between open and closed, about 0.5 or 0.6 ohm, which many meters at that low a resistance don't reliably show.
A basic continuity test of the low tension, primary, winding can be done by measuring from the cb centre screw to the armature spindle, or mag body if it's assembled with the earth brush fitted. That should show you your 0.5 or 0.6 ohm low tension resistance. Primaries very very rarely go wrong unless a wire breaks off inside.
The HT winding should show, round numbers, about 5000 ohms if you measure from the brass section of the slipring (after taking a pick-up off and turning the mag till the segment is visible) and the mag body, armature spindle etc. If there's no continuity there then either the coil has a break in the HT winding or its connection to the slipring is defective. The winding has a 'spike' on the end which just goes into a very tiny hole in the slipring and touches the inside of the brass strip mentioned, to get the energy from coil to plugs via the pick-ups and brushes.
So the primary coil generates its small AC voltage as it rotates, assuming there's a reasonably decent magnetic field. K2Fs are good at retaining magnetism, but if there's no 'flip' every 180° as you turn the thing by hand, not good. When the points open, HT voltage is induced in the secondary winding. The earth for both windings is common, at the condenser end. Both windings plus the condenser are earthed by a 5BA screw into the brass end cheek.
The condenser is the thing that would benefit most from a megga or insulation tester, but it needs to be disconnected to test it. If it's an original it will certainly have deteriorated. Testing capacitance just needs a meter that has that function; testing for leakage involves putting the insulation tester across the two sides (live and earth), choosing your voltage setting and seeing how much it does or doesn't leak as that voltage is applied. A good test would show, say, 2 Giga-ohms at 500v. A vicious test might involve applying your 1000v, but I wouldn't go that far! If you're lucky, an original might show you a few kilo-ohms of 'leak-proof', at 250v. All too often, it'll show nothing or near enough, and its capacitance can't be measured. The voltage rating of any condenser being tested should be respected, in case the internal insulation is damaged by overdoing things. Many of them allegedly 'self-heal' if perforated by unusually high spikes, but there are limits to how much they will withstand.
If you can be bothered you can create the Lucas coil testing set-up explained in those Workshop Instructions - but absent HT continuity I wouldn't bother, although it's handy to have a test rig, obviously.
On the bench, a K series should easily make fat sparks that go 'clack' at the flick of a wrist. Turning steadily at about 130rpm it should make almost all its sparks, with big gaps of 5.5mm. A really good one will do a fair bit better than that (I've seen 100% sparks at 100 rpm now and again); a dying one might need several hundred rpm to do anything, or may do nothing. All depends what is actually up with the thing. A low tension fault or assembly error will kill anything stone dead - but a dying HT side will often do a bit, cold, at certain speeds, maybe!
Good luck as you proceed!
-
Simple one this time , what is the current spark plug to use
-
Thanks Grolly, I have niether of the fibre insert insulators but do have the fibre parts that go where your capacitor goes, I dont have the plastic dimple instaed I have a little steel ball bearing under the clip so obviously this has been messed about with I have sent for a complete contact assembly and longer bolt so hopefully that willl sort things out
Devlin
-
For the plug, I'd say NGK B6HS, short reach no resistor, for iron head engines. Others may have more specific advice for early A7s and there are equivalents from other makers. My iron A10 ran NGKs mostly but I also had some Bosch W7AC at one point. Champion do the L86C, and there be a good few others.
Those tubular fibre insulators are essential, or the cb centre screw and / or the second small retaining screw will almost for sure short the live point to earth on their way through. The little screw also needs a fibre washer under its head to complete the job. The mag will very probably be a spark-free zone if they're not there. Fiddly to make and not that easy to find, so if you've got a complete assembly coming, well done.
The less wobble of the opening point on its pivot post, the better, so with any luck the new one will be better than what you have and won't need a ball bearing!.
-
After a visit to Priory Mags website and a hour or so reading I have decided that to go the easy cap route I first need to sus out what blob of solder is what, I have three so one will be the earth and the others will be the winding ends and I assume one blob will have 2 wires and one will have one I also assume that the blob at the slip ring end should be ignored as the original capacitor is at the other, so I have 2 options desolder the bigger blob hoping it has both ends of the windings or wait till I get a small bearing puller and had the bearings off, does anyone agree with my assumptions
Devlin
-
With the armature out, as original there are two visible wires at the condenser end, one visible wire at the cb end (where the low tension live connects to the cb centre screw), and then there's the HT end that disappears into the slipring. The wires at the condenser end may not be visible if they have been buried in resin if a replacement capacitor has been fitted in the past.
The earth low tension and capacitor earth, and HT earth, are all done in one; the other side of the condenser has a live wire with 2 internal strands in it. One strand is straight off the coil, the other goes from the condenser to the cb end via a channel that goes back along the length of the bobbin. If you've got an original, then there will be blobs of solder covering the heads of the 5BA screws that attach the condenser to the armature.
To identify which wire is which off the coil at the condenser end, it's easier to have a look at some pix. Whatever way you want to go on sorting it, the orientation of these things is always the same on the inside. So here's a description and pix of what's what. Different mags are covered but there's plenty on K2Fs:
http://www.brightsparkmagnetos.com/condensectomy/index.htm
While self-interest says I naturally wouldn't want to dissuade you from using an easycap, I think you really need to know whether the coil is any good as the number one priority. It's the expensive bit and it's a PITA to have to do things twice. I'd be pleased if you bought a condenser, but I wouldn't feel good if it didn't help.
Whether it's worth a go depends how much you like playing with these things! But I would certainly want to see it running on the bench - hot - somewhere close to the Lucas spec before putting it back on the bike, otherwise you'll get more practice than you might want at extracting pinions and retiming the thing!
-
I finally got the capacitor end off the armature and have two nice clean copper wires poking up, however when I put my meter across them I get various readings from open circuit to .60Mohms to 17.61 Mohm then back to open circuit IR is good at 200ohms @100 volts, unsure if the coil is is holding the small applied current and no idea what I should be looking for and should I get any readings at the HT spike
Devlin
-
I finally got the capacitor end off the armature and have two nice clean copper wires poking up, however when I put my meter across them I get various readings from open circuit to .60 ohms to 17.61 ohm then back to open circuit IR is good at 200ohms @100 volts, unsure if the coil is is holding the small applied current and no idea what I should be looking for and should I get any readings at the HT spike just tried diferant clips and getting consistant .63 ohms
Devlin
-
Blimey! Assuming you're getting the meter onto the strand of the 'double strand live side' that is from the coil, you should see half an ohm odd between it and the 'other' low tension wire, which is the earth. That's the primary winding, same as measured across the open points when all is assembled.
If you're not getting onto the strand that comes off the coil - but are just touching the strand that goes to the cb end, now detached from the other strand - then you'd see Open Line or loads of mega ohms. (Edit - I read your 'Mohms' comment, not the repeat where the 'M' had gone.)
Suggest you ensure that the two strands on the double strand side are properly soldered together after the disinterment and check again, or if they are separated, try from each strand to the earth side.
No need to be applying any volts or current to measure the coils, just use the Ohms scale.
If you were putting the meter across the condenser by any chance, on the resistance scale, you'd see a rapidly rising number that stopped at Infinity - as the meter's battery tried to charge the condenser up. But I don't think you're doing that if you're 'on the wires' and they're not connected to the condenser?
For the HT, you should see the several thousand ohms mentioned from either the earth low tension tail to the HT spike / slipring brass or from the live strand from the coil to the HT spike / slipring brass. Again, simple resistance, no applied voltages or anything.
-
Thanks, Yes its across the "twin" wires and the single at .63 ohms so not far out I will zero the meter once more before I recheck I will solder the ends of the live together as I cut the blob off and I will recheck the HT spike to either or both tomorrow
-
Myabe somme ideas to be picked up in this topic. f.ex checking left-right timing.
https://www.a7a10.net/forum/index.php?topic=1375.15
-
Another quick question, can I put the A/R unit in the sonic cleaner as I am unsure how the fibre gear will react to carb cleaner solution
Dev
-
G'day Devlin.
Although the ultra sonic won't hurt it the "carb cleaner" might. What medium are you using?
Give it a go with just hot water and dish washing soap. I know it won't hurt rubber/plastic.
Cheers
-
Thanks, reason I asked is it started to soften the gear lever rubber, although that is probably starting to break down anyway given the age
-
The magneto is sparking once again a big thanks to all the members on here and a huge thanks to Bill Brown at Brightsparks also Paul Wolf who rewound the bobbin to suit the easy cap, learning curve for sure but the satisfaction of achiveing a positive outcome is priceless
thanks again ]
Devlin