Fitting alternator and rotor to G12

Information relating to the Matchless G12 or AJS Model 31 650cc twin
Spock
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Fitting alternator and rotor to G12

Post by Spock »

I asked on taking my G12 primary casing and alternator off to replace about the order of the washers and packers and was assured here that the domed washer went on the outside.
This has been annoying me as it didn't seem right and the rotor didn't line up with the stator properly. Now having the new rotor and stator I find that the new one is thinner than the old and doesn't line up with the stator (probably the reason it wasn't charging well in the first place)
Anyway, having scoured the various diagrams and books I have come to the conclusion that not only was mine probably assembled wrongly, there are parts missing.
The pic where the domed spacer is outside the rotor is how mine was assembled, I am pretty sure it should be on the inside of the rotor as per the other pic.
Picture 006.jpg
The thin washer I am not sure of even whether it should be fitted as I cannot find it in the parts book or exploded diagrams. The lock washer was missing.
The nut will not tighten down on the new rotor as it is slightly thinner.
The question I have is- does the domed spacer go on the inside as I now think and what additional spacers do I need to push the rotor out further to fully centralise it in the stator?
Also I see a lot of comments about centralising and adjusting rotors, there is a tight location for the stator (I had to press fit mine) and the rotor is fixed on the shaft. Assuming that the components are within tolerances (and checking this) what adjustment is there?, there is nothing that can be moved?
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Duncan
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Re: Fitting alternator and rotor to G12

Post by Duncan »

As per the second picture:
http://archives.jampot.dk/technical/Cut ... 7-1964.jpg
Upside down!

The loose washer is not standard but may be required if the thread depth is not enough for the breather, if I remember correctly there should be a lock washer under the breather.
Spock
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Re: Fitting alternator and rotor to G12

Post by Spock »

The diagram you mention is the best source for the part order on the shaft but as you say doesn't show the thin washer. However when I measure the centre of the stator compared to the middle of the rotor it seems there is a packer required to make them align, particularly now I am fitting an RM20 which is thinner than the original.
However I suspect that the reason the bike never charged properly from the day I got it was that the domed spacer was in the wrong place and the original rotor/staor alignment was wrong which gave a poor output!
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ajscomboman
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Re: Fitting alternator and rotor to G12

Post by ajscomboman »

I have stated many times before that the domed washer goes next to the sprocket followed by the rotor leaving the flat face of the rotor facing outwards. This then allows the locking washer to be fitted correctly onto the face of the rotor and finally the breather nut which can then be locked in place. If you try to fit the domed washer on the outer face of the rotor with the domed face outwards it doesn't allow the lock washer to work correctly and as you rightly have stated it off sets the centre line of the rotor in the stator. I think what confuses people most if the fact that the Lucas brand name has to face in to the engine and many think that is wrong and the name should face outwards.
Spock
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Re: Fitting alternator and rotor to G12

Post by Spock »

That raises another query, mine was fitted originally with the Lucas branding facing outwards. I had thought it a bit odd that the scribed timing marks were on the inside but assumed that the original fitment, and advice on the interweb, was correct as there is a common thread throughout all the online documentation and advice saying that the lucas is fitted outwards. Is there a definitive manual or manufacturers guide that says which way round they go?
I have found references to a spacer for fitting the rotor in triumph forums numbered 71-4435, it doesn't seem to be widely available but is for fitting RM20 rotors to bikes where the rotor is misaligned due to the narrower width.
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robcurrie
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Re: Fitting alternator and rotor to G12

Post by robcurrie »

Here are photos of the installation on my 31 CSR, Lucas facing outwards, lock washer doing its job and thick washer between sprocket and rotor.
20170218_154706-1328x747.jpg
20170218_154642-1328x747.jpg
Rob C
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ajscomboman
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Re: Fitting alternator and rotor to G12

Post by ajscomboman »

Rob has your rotor dished faces both sides as the domed spacer should fit into the dished face. The locking washer shouldn't be dished to fit as it should sit squarely on the flat shoulder of the rotor with the little locking tag slipped into the grove on the rotor where the woodruff key slot is machined. The nut then is threaded on which locks down squarely onto the washer (the little tab holding it in place from turning) and is bent up onto one flat of the nut locking it in place.
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Re: Fitting alternator and rotor to G12

Post by robcurrie »

Just took it off to look. The rotor and thick washer are flat, the dished washer has a tab to fit the key slot.
20170218_180118_crop_761x720.jpg
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ajscomboman
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Re: Fitting alternator and rotor to G12

Post by ajscomboman »

How interesting, that's a setup I've never seen before. My alternator twins have always had a domed thick washer as per the parts book and a lock washer that is totally flat with the little locking tab on which as you can imagine is why I've always set it up with the Lucas name facing inward. Measuring the centres it's always been nearly smack on the centre of the stator.
Spock
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Re: Fitting alternator and rotor to G12

Post by Spock »

Just to avoid confusion.
My original rotor had a flat side and a dished side. I am pretty certain now that the rotor was fitted the wrong way round with the flat side to the sprocket and the dished spacer under the retaining nut with no lockwasher. This misaligned the rotor with the stator and was probably the reason for the poor charging (and the eventual probable falling off of the retaining nut at some point in the future!

The new stator is thinner and has dishes on both sides. I can fit it either way round. It is still needing to be packed out further even if I move the dished spacer to the inside as it is thinner. I have seen references to this packer on triumph sites. My question is, does anybody have first hand knowledge of fitting an RM20 stator to a G12 and how did they do it with what parts...........
Locked