Strange magneto fault

Thread Starter

Kennytoo

Joined Dec 23, 2015
5
I have a magneto question. I have a Victa Twin mower. These motors had problems with their ignition coils. esp. peculiar behaviour. Right now, I can get the motor to start, but only if I disconnect the front cylinder plug lead, fit another spark plug to that lead, then ground that plug on the mower base. It will then start immediately on the other cylinder and run well on only the one cylinder. If I can do it quickly enough, I can flick the 3rd plug off the lead at high revs sometimes and put it back on its proper engine plug, and it then continues to run correctly on both cylinders, but if I miss doing that quickly it stops. I have an Atom, twin electronic module fitted and it works ok on the other twin I have, so the problem is not with it. It must be some sort of coil problem, but what is likely to be i?
 

Thread Starter

Kennytoo

Joined Dec 23, 2015
5
Here is a photo of it with the 3rd extra plug attached and earthing on the base plate of the mower. For the first plug, it is under the cowling at the front but can't be seen, tho' the lead attaches to it easily under that cowing.. What is happening is crazy to me because if it starts on the back cylinder (to the right of the photo under the cowling) on its plug, with the other ( the 3rd one) grounded on the base of the mower, why not when earthed too when its lead is attached, via its own plug when connected? I've used magnetos for years and have never encountered anything like this before, except on several Victa twin motors with this type of coil spark problem. IMG_0484.JPG
 
Last edited:

m3vuv1

Joined Dec 11, 2018
46
is it a double ended wasted spark type coil?,if so one plug will run at the wrong polarits and wear at different times,ie electron search path times differing etc.
 

Thread Starter

Kennytoo

Joined Dec 23, 2015
5
The coil centrally is mounted on a 3 legged, W shaped metal unit which gets set very close to the spinning magnets. It has twin spark leads from each side of the coil and a third point at the back to. which a wire goes to either, one set of points, or an Atom twin spark electronic module which can replace the points. These coils had a bad reputation for failing totally as well. But why it works ok on the other plug, when I do this disconnection of one lead, and fit a 3rd plug, earthed on the base, and the motor then starts on the other cylinder, is baffling. It seems that by connecting the leads to their own plugs, somehow, it shorts both out , thus not sparking at all as it never fires either cylinder then. The only thing I haven't tried yet, is to get it running with no plug in one loose lead to see if it would start anyway, then if it did, I'll when try to fit it and keep it running. But I have noticed that if the 3rd plug isn't earthed properly, it won't start. But I will try it tomorrow anyway. AS for questions of polarity, that should be correct for whatever it is, as on my second mower, all is set exactly the same, and with its good coil, it starts readily.



is it a double ended wasted spark type coil?,if so one plug will run at the wrong polarits and wear at different times,ie electron search path times differing etc. Would compression make it difficult for the spark to jump on the plug when both are connected?
 

m3vuv1

Joined Dec 11, 2018
46
had a bsa A10 650 years ago,would cut out when hot,had a good spark with the plugs out but nothing under compession,had the mag rewound for nearly£300 that curred it,it was the windings breaking down when hot,had me foxed for a while tho!
 
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