SR1 Magneto Identification

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leobailey
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SR1 Magneto Identification

Post by leobailey »

What is the correct Lucas SR1 magneto for my 1959 G3. (i know someone will shout it's coil ignition)

I already have the correct cams, sprockets, chain, advance unit, timing covers and all of the magneto platform nuts bolts and fittings. The only thing missing to set it up as magneto ignition is “the correct SR1 Magneto”

I have attached some plate detail photos from eBay, one appears to be clockwise rotation , the other ant-clockwise rotation.

Do all the drive ends look the same with the words ANTI on the left hand side and Clock on the right hand side

Can you help me easily identify the correct SR1 for the G3 setup.

Leo
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Groily
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Re: SR1 Magneto Identification

Post by Groily »

Not completely certain what exact Part Number is 100% correct for the model and year Leo.
But any anti-clockwise drive one, probably MK 11A, (with the 4 x 1/4 ww threaded hole mounting in case there are any variants in the world of stationary engines, other marques etc) would be fine. Not sure if they are all marked clock- or A-CW on the castings. There are tiny differences between models and it's hard sometimes to know what is what as things get different bits added or swapped in over the years.
Some people prefer the mags with the metal end covers (which might not be Mk 11s, I'm not sure), some prefer the plastic (because there's no chance of a hidden short to earth from the low tension wires against the inside, which does happen).
The important thing is to get the rotation right, and make sure it's a decent runner.
The detailed info I have pretty well stops at the end of '57 - but some SR1 applications are listed in the Lucas parts lists for pre-'58, for 500s but also for some 350s as well. There won't be a lot of difference in spec I don't think, between then and yours.
See, eg, info in the Archives or here: http://www.brightsparkmagnetos.com/libr ... 20ATDs.pdf
The id tag / stop button can be stamped any which way a person wants of course . . . and many probably have been stamped to say something different from original, or simply swapped betweeen instruments. The 12 63 in one you show is December 1963. The first one is November some-I-can't-read-it-year-in-1950s
So really, the only obvious tell-tale difference between models would be the end cover I reckon, plus whatever was stamped on the label. BUT, for Perfect Original and a 100% Definitive Answer I think you'd have to scour the Archives or any other sources out there, or find a known-original beast with its known-original magneto in place, and see what the serial number is. I'm sure there are a good few in the hands of people on here!
alanengineer
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Re: SR1 Magneto Identification

Post by alanengineer »

A Magneto aimed at being fitted to a motorcycle will not have the 'button to stop' The label might still say it.(like the first photo).. Dumper trucks, lawnmowers, stationary engines have the 'button to stop' fitted. you can reverse the rotation and you can take off the button, but you need good stuff inside the body and a new coil is expensive.
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leobailey
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Re: SR1 Magneto Identification

Post by leobailey »

Thanks for all the advice and the leads to other information. The "push to stop button" is as you say a good indicator that it's not from a motorcycle (lawn mower, stationary engine etc.).

In my mind I'm convinced the correct rotation for the G3 would be anti-clockwise ?

If I come across a goodish one that is the wrong rotation, does anyone know the ease or feasibility of reversing the magneto's rotation direction

Leo
Mick D
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Re: SR1 Magneto Identification

Post by Mick D »

Hi

I don't know the vintage of your earlier parts but the last magneto fitted to a G3 was on the 57 model:
57 Mag.png
Regards Mick
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alanengineer
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Re: SR1 Magneto Identification

Post by alanengineer »

their is a lucas service sheet that explains what to do. Its on the internet somewhere
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spookefoote1956
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Re: SR1 Magneto Identification

Post by spookefoote1956 »

Does yours have a valve lifter?
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leobailey
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Re: SR1 Magneto Identification

Post by leobailey »

Hi Chris, mine does have a valve lifter/ de-compressor

To everyone else out there, so it is relatively easy to change the rotation of an SR1 or is that itself a bit of an over simplification

Leo
alanengineer
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Re: SR1 Magneto Identification

Post by alanengineer »

Hi Leo.
It is a simple task. Only if you can read instructions and do the task as described and have the tools appropriate at hand. If memory is still working, you will need a certain size drill to use as a spacer.
Read the instructions and judge for yourself if you are capable. Old dumper truck ones are half the price of motorcycle SR1s
raffles
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Re: SR1 Magneto Identification

Post by raffles »

I beg to differ my 56 g80 is all original and has a stop pad or button or whatever you wish to call it.It was on the bike from day one
Tony
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