Hi all and for some-welcome back from the cold..

I think it was discussed here before,
But just to be sure:

The magneto on the left is the correct one for the M20, with anti clockwise rotation when looking from the shaft side,
And the one on the right is marked as clockwise rotation, the pickup is on the other side, and the points advance/retard would be of a “slack” type if used on the M20.

Can the left one be fitted as-is?...

Thanks,
Noam.

email (option): noam10@gmail.com

Hi Noam..The left hand mag can be fitted straight on 'as is', though the mag body casting is the post war type so strictly speaking not correct for a WD bike. The right hand one, if it has four tapped holes in the base is probably for a Norton, also post war...Ian

email (option): ian@wright52.plus.com

and boy, did slack wire advance confuse me on my first norton....

email (option): chris.astinbarker@btinternet.com

Hi Ian and thanks.

Yes, the right (Wrong ) one does have 4 peg holes.

So again a few questions if I may:

1. What is the difference between the wartime and post war mags? (I took the left one off a "green" engine)
2. So, as the right one has the holes, can I use it for a WM20?..
3.What should be the measure of the pegs? around 1/4" or 3/8" x 1/2"?

Thanks,
Noam.

email (option): noam10@gmail.com

Hi Noam..On the wartime mag bodies the curved part of the body the dynamo sits on runs along the whole of the mag body and meets the vertical rear face of the drive end housing, so there is no gap under the dynamo when it is fitted.
The pegs in the base are a 3/8 whitworth thread into the body, reduced to a 5/16" diameter shank to fit the location slots in the crankcase...
You wouldn't be able to run the Norton mag on the M20 as it would be working the wrong way when you use the adv/rtd cable.(ie retarding not advancing). If you set it up to work the other way the fully advanced spark would not be at the point of maximum armature flux...Ian

email (option): ian@wright52.plus.com

As always Ian,
Thanks allot !

OK, it would be a shame not to use this mag, as it's
a good NOS with a strong magnet and the armature also appears to be nice and healthy,
So I will try to plant it into another body..
(I know you must drive it around and test if it doesn’t lose the spark when hot)

Cheers,
Noam.

email (option): noam10@gmail.com

I have had a few NOS magnetos and all failed when I started using them. They do have a limited shelf life.

Did anybody try these magnetos? http://bt-h.biz/mag-dyno.htm

Henk.

email (option): ahum@quicknet.nl

I never knew that post war mags have different bodies. Few years ago I bought rebuilt mag from De Groot and sent my wartime mag for exhange. Now I realize that they sold me postwar one:(

email (option): kalle.tikas@gmail.com

Henk, had mine rebuilt and it made it a first kick starter. But if I were to purchase one of those new ones, I would make sure to remove it when time comes to sell the bike and sell it seperatly to make sure to get my money back. Some of the selling prices on the WM20 are only twice the cost of one of those mags.

email (option): unpob@yahoo.com

Noam, why not look at the date on the magnetos??

It's stamped on the tag!! a month/year code if I remember well.

If the Norton was the wartime one I'd have traded you for an N.O.S. WW2 BSA housing.

Btw. the Norton does not have a slack wire advance standard!

Cheers,

Lex

email (option): Welbike@welbike.net

Well blow me down with a feather!
I've been accumulating magnetos for my WD/CO's and post-war model G's for ages now and didn't ever pick up the difference! I just popped out to the shed and had a look in my "electrical bits" cupboard and thankfully noted that a good few are the earlier types. In fact, one is dated 137 which is a pre-war job if the plate can be believed.
The shelf is a bit crowded, so I couldn't do a proper stock-take, but I counted 4 oldies within easy reach. So at least I can mount the correct pattern if ever I get to complete one of these things! Long overdue now.
I'm still chuckling!!!!

email (option): brucekirby@telkomsa.net

Ok question then. the magdyno i got front you Ian looks like the one above with the ht pickup on the right and the advance on the right. the magdyno that is running on the bike looks like the one henk posted. pickup on the right and advance on the left. this is on a 1941 royal enfield wd/c. which should it be abduction what is the effect of having the advance on the wlong side.

email (option): v8zspeed @ yahoo.com

Hi Jesse..The positioning of the adv/rtd cable makes no difference to the function of the mag as long as the direction of rotation of the unit is correct for the bike.
What it does do is reverse the operation of the handlebar lever..so if the bike is fully advanced with the cable 'slack' (which the Enfield is), it will change it to fully advanced with the cable pulled 'tight'.
The problem now with both Enfields and Nortons is that the points end casting with the cable entering on the left of the contact breaker as you look at it is becoming hard to find..Ian

email (option): ian@wright52.plus.com

Ian. thanks. so its the correct one then. When the time comes i am better getting it rebuilt.
thanks

email (option): v8zspeed @ yahoo.com