Fixing wico series a mag.

Pretty good instrument the Wico A. It should feel sort of 'lumpy' to turn over with max resistance felt just before the points open. If it hasn't been 'got at' probably 75 % of trouble on these mags turns out to be no more than mucky or corroded points. If they are really corroded (covered with a sort of white fluff) they will have to be removed and rubbed clean on a sharpening stone or similar, but first try nipping a small piece of stout writing paper between the points and wiggling about a bit. Repeat 'till the paper comes out clean.

If still no luck primary and secondary windings can be tested for continuity with an AVO meter, I can't really remember what the resistance of each should be, but probably a few tens of ohms for the primary and a few K for the secondary.

Yes the condenser can be unreliable (our resident expert on such things, Arthur Griffin claims never to have found a good one) but this usually results in a weak spark rather than none at all.

Good luck!

Ps. What's the engine

Reply to
Nick H
Loading thread data ...

Hey , This is the first stationary engine I've attempted to retore . I'm trying to get the magneto working but to no avail . I understand the basic principle behind a magneto and the one I have seems in quite decent condition it turns over easily and is well oiled . However it does not create an output voltage of any kind ! I had read that the capacitor in a magneto is the most likly part to deteriorate , is this correct ? If so how do I go about testing it to see if it holds charge ? Also is there a way to test the integrity of the secondary coil ? as this may also be a problem . Any other tips on likly problem areas would be greatly appriciated . Cheers , Max (18)

Reply to
Max Wilkinson

Thanks for the advice , the Engine is a Petter A type , air cooled by fins on the flywheel . A friend of my dad restores vintage cars and he used to put the mags off those in the oven to dry them out . Will this help at all as there is a chance the mag could be slightly damp ? The engine seems to have been used to run a circular saw as there was alot of oil soaked sawdust on the engine . Finally how do I remove the flywheel from the shaft ? Cheers , Max

Reply to
Max Wilkinson

It'll certainly do no harm, though I would be more inclined to leave it on top of the central heating boiler for a week.

Brian L Dominic

Web Sites: Canals:

formatting link
of the Cromford Canal:
formatting link
Light Railway:
formatting link

Reply to
Brian Dominic me

Hi Max, in my experience, once you've established the points are clean and all the connections are good, the next thing to check is the coil.

Usually the HT section (the part which connects to the sparkplug) fails by going open circuit. Measure this between the "pip" on the winding which the plug lead terminal connects to and the common (that connection on the coil which connects to the metal body of the mag. If this checks out, check the primary (between common and the other lead on the coil). The resistance figures that Nick quotes are in the right region, though IIRC the HT section (also called the secondary) is between 10 and 15K. Do disconnect the capacitor (or condenser, whichever you want to call it) before doing your measurements. You cannot easily test the capacitor without special equipment. I can, and all of the old Wico A caps I've tested are poor, though in most cases they didn't cause major problems.

As Nick says, a duff capacitor is more likely to take the edge off the spark rather than kill it. If it failed short circuit, it would kill the spark, but usually these caps just get rather poor in insulation resistance value, rather than short out.

As for drying the mag out, if the coil has failed open circuit, you won't improve matters. If you test the coil and it seems good, then I would keep it out of the heat, as sudden drying of the shellac insulation can cause shrinkage and movement which could lead to breaking the very fine copper wire in the coil.

Hope this helps, Arthur G

Reply to
Arthur Griffin & Jeni Stanton

Cheers guys , hopefully I'll have it sparking in the next few days :D


Reply to
Max Wilkinson

With difficulty as they are often rusted badly, although the oil/sawdust mix may have saved it. Assuming that you have the pulley key out and the pulley off, the next step is to remove the flywheel key which is recessed below the flywheel rim. A key drift would be handy but in its absence something with a slow taper and either short enough to fit within the flywheel or cranked. A large steel chisel or perhaps the end of a pry bar ? Before applying heavy hammer blows (light ones achieve nothing except damage) to the implement give the crank/flywheel a long soak in your favourite release agent. Best to turn the engine on its side and build a dam for the penetrant from putty/blutack WHY As a last resort you may have to drill the key out the remove the flywheel/crank/main bearing assembly as a lump. Then use inertia. i.e drop the lump onto a hardwood or lead block resting on solid thick concrete. I'm sure others will expand on or correct the above Finally is it essential to remove the flywheel ? regards

Reply to
Roland and Celia Craven

I guess it isnt essential to remove the flywheel , however the protective guard around it has been quite badly bent (due to the engine being rested on it) and thus rubs against the flywheel . Its seems like a hell of a job to get a flywheel off so I think I'll try and manipulate the guard into something like its original shape . Cheers , Max

Reply to
Max Wilkinson

Whilst agreeing with the others who've commented, I'd still offer my two penn'orth ;o))

I've developed a real thing about points since I've had much to do with stationary engines. The other device that used magnetoes was bikes and because they were designed to live in the open air, the mags are better protected from the damp with better sealed end caps etc. It has come as a surprise to me to find that EVERY set of points I've found on a stationary engine wot has been stood are oxidised. You can't see it with the points in place, so take them out, making sure you record where all the washers go to maintain their insulation upon re-assembly.

If you look at the polished working face, you will probably find a thin, hard layer of white tungsten oxide, an extremely good insulator. Take a piece of 400 grit Wet 'n dry paper (or finer) and stick it onto a bit of glass with water. Holding the point as flat and straight as you can, face it off until the white oxide has gone and the metal face is shining. Don't try to get all the pitting out, fine in an ideal world, but not so good now new ones are hard to find. Repeat on the other one.

Refit the points and gap them with the heel of the moving point well onto the cam. 12 thou (or the thickness of a postcard) will do fine at this stage. Spin the armature and see if you've got a spark.

Yes? OK, see if the engine goes!

No? Put the mag on the grille at the back of the fridge, on a shelf in a warm room or wrapped in newspaper in the airing cupboard. Leave it for a week and try it again.

You may very well snap a winding wire or melt the insulation if you put it in the oven - it gets bloody hot in there! Gentle heat is what it'll need.

When you get the engine running, leave it running for at least an hour to get it up to a reasonable temperature. When you put it away, you could do worse than taping a plastic bag around the magneto.


Kim Siddorn,

Reply to
J K Siddorn

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.