Petter A Series II - Wico A Magneto Issues

Hi,

After a carburettor strip down and thorough clean plus new float and gaskets I have had my recently acquired engine running but not long enough to get it warm and optimise the mixture.

I have since removed the Wico A magneto (A10578) checked and refixed the HT connection, cleaned and reset the points.

However, bench testing it in the vice I am getting intermittent sparks at the plug.

Could this be a condenser issue or a more serious coil issue?

Any advice or assistance would be much appreciated

If you have a multimeter, check the resistance of the  HT coil - should be around 5000 ohms. Another way is to use a low voltage bulb and battery to check for continuity. If it shows open circuit then it may be there is a break but the voltage is high enough to jump the gap internally. 
I also had a similar problem and found the cause was an intermittent short on the contact breaker.
Good luck.

Woodsman,

Thank you for your reply and suggestions.

Bear with me I am a mechanical engineer - but using my multimeter on the coil between the black coil lead and the HT output tab I get a reading of between 0.004 and 0.005 on the 2M ohm scale (which equates to between 8,000 and 10,000 ohms).

Regarding continuity between these two points instead of the normal buzzer on my meter I get a reading of 1.972 - not sure what this means?

I look forward to your thoughts.

Apologies - I should have been more precise.

Measure HT coil resistance between the tab and 'earth'  i.e the body of the mag with the HT lead disconnected from the plug to ensure coil is isolated. That said the the resistance looks OK  (I was thinking of a Villiers coil)

By 'black coil lead'  do you mean the wire that connects to condenser and contact breaker ? Bear in mind that if the points are closed that's effectively earth. Stick a piece of paper between them and check that the arm that sits on the insulating pillar is not earthing anywhere.

Have you made sure the points are nice and clean and correctly gapped.


P.S. I took the liberty of deleting the duplicate post

If it proves to be your coil and you can't get one my modification is tried and tested.
https://ukengineforum.forumotion.com/t10816-wico-a-series-magneto-with-bsa-bantam-coil

Paul,

With a piece of card between to points I have retested between the HT tab on the coil and the magneto body and I am getting the same readings which indicate a resistance of 5400 ohms (using the 20k and 200k range setting on the multimeter).

I had already cleaned and reset the points but checking continuity in this area with the multimeter there could be an issue.

I do seem to be getting a continuity between the moving breaker arm metalwork and the body of the magneto.

I have a new set of points plus a condenser on order so will disassemble and check what is going on in this area.

Look forward to your thoughts.

David P

Andy, thank you for the Bantam coil replacement link - looks a neat and proven solution to a coil problem. The sourcing a replacement 'like for like' coil does appear to be a bit problematic.

Bantam coils can be found for under £15 delivered on eBay if the need arises.
Just a thought, is the insulator strip properly in place between the points sprung strip and the mag casing?
Good luck.

Good call Andy, had the same problem once. Insulator strip missing - replaced with a strip cut from yoghurt pot.

Paul/Andy,

Thanks for the advice.

Checked this morning and the black square insulator is in position below the moving point metalwork and no leakage to earth.

However, after some YouTube tuition I tested the condenser and I believe this could be the culprit. On the 20M ohm range on the multimeter on a good condenser you should get a low reading rising to a high reading.

So awaiting the delivery of a new condenser with interest.

Paul/Andy,

Sorry, I misunderstood both of you.

I have just noticed the black isulating strip fitted between the breaker point sprung strip and the magneto casing.

Mine seems to be made of 'plasticard' or a similar material but it is in place.

You learn something every day!!

djpeng wrote:You learn something every day!!

That's why we all here.

Just an aside, reading capacitors/condensers with a standard multimeter can be hit and miss but for a few quid and not expensive you can buy multimeters with a capacitor testing point in the body which will give you an accurate reading.

Maryalice

The DM6013L capacitance meter is a good value tester to keep in the toolbox/workshop, example: Ebay item No.373147499286

Some good news and some bad news regarding my magneto.

New condenser (fancy new type X1413 encased in black plastic) new points and spark plug arrived and were fitted.

Good consistent spark every time on the bench.

Fitted magneto to the engine and was hoping for a successful outcome - after a few attemps not a hint of firing. Took the plug out and checked for a spark whilst cranking with the plug against the magneto casing - nothing!!

Removed the magneto from the engine and found the shaft had sheared off behind the impulse coupling (see photo).

I am wondering if there was perhaps an issue within the implulse coupling as it was quite difficult to rotate on the bench at times.

So now need to either get a replacement type A10578 magneto from somewhere or try and find a replacement rotor shaft!!

David P

Oh dear, was the impulse arm free to move and 'flop about 'readily?

Alan

I can't imagine how that could happen, is the Bakelite coupler still intact?

Depends how desperate you are to make an offer on this.
https://www.ebay.co.uk/itm/115366955845

Andy,

Thank you - I did see this on eBay last evening and it looks the right one - I have asked the seller for confirmation of the type number before I consider making an offer.

It is a mystery to me as there cannot be a great deal of torque required to turn the rotor in the magneto itself so can only think that it was a lateral load caused by an issue within the implulse coupling.

It was quite hard to turn over the impulse when testing for a spark by hand on the bench but not unduly so - the striking lever seemed to be moving freely.

Not really understanding what the mechanical implulse actually does - it can only change the spark timing I am guessing?

The floating coupler (Bakelite?) on the engine side seems to be intact.

David P

Andy,

Thank you - I did just find that online.

I also downloaded a copy of a very good article here:

http://www204.pair.com/bbg46/FM%20Mag%20Manual/Mag%20Impulse%20Couplings(43-48).pdf

Another learning experience!!

David P

I've never seen a Wico A magneto rotor shaft with a fatigue crack like that. Very unusual, and unlucky for you.

I have a Wico A1057B on the shelf if you need one, good spark on the bench.

Blue Cat,

It is difficult to understand why this occured - the pawl in the implulse coupling is moving freely and there cannot be much torque required to turn the rotor itself.

Thank you for the offer of a magneto.

In desperation I have already managed to source what I hope is the correct one on eBay for a price!! Nearly half of what I paid for the complete engine.

If it is not the correct model I will resell it on eBay (as there seemed to be plenty of watchers) and might take you up on your offer.

David P

There is a complete engine at £100 on eBay but the problem is always location location location.

Update on magneto issues.

The replacement magneto that I purchased on eBay is the correct one (A1057B) dated 1952 and seems mechanically OK and the impulse mechanism is certainly easier to operate by hand.

However, this still does not explain the rotor shaft breakage on the previous unit.

The coil on this magneto is reading a resistance of 5.24 on the 20K ohm range (0.52 on the 200K) - is this about right?

The previous magneto was reading 5.47 on the 20K ohm range (0.54 on the 200K).

I have replaced the points and gapped them correctly at 0.015". Have fitted the new X1413 condenser (plastic encapsulated type) but still still not getting a constant and strong spark at the plug when bench testing.

Awaiting delivery of an analogue multimeter that might be a little more sensitive for my needs.

Andy - what resistance do you get across your Bantam coil?

I can’t answer that for you until Friday

Andy,

Thank you - the weekend will be fine.

I just need some sort of reference point for a coil that is working well.