G80 DYNAMO NUT

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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G80 DYNAMO NUT

Postby Rupert123 » Mon Jul 22, 2019 12:58 pm

Hi,
I suppose you heard this old story before , whilst trying to fix an oil leak on my tin chaincase which i have made ten times worse , with the outer case off i noticed the dynamo sprocket nut was worn on the end it had been rubbing somewhere i undone the nut with my fingers no circlip, no lock washer no loctite ,i took the dynamo off
to check the shaft and key, which was poorly fitted it looked as like there were some problems before hand the dynamo sprocket was bruised at the back where somebody was belting it off with a hammer.
I would just like to know what does the circlip do, does it go behind the lock washer also round the rear of the dynamo there is a band about 3/4" wide it clamped around the diameter with a screw and nut is this the stop
that prevents the dynamo moving too far inward.
The bike is a 54 g80,gearbox is GB26G54 and the dynamo is E3ARA05-K.

Kind regards
Martin.

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Re: G80 DYNAMO NUT

Postby Rob Harknett » Mon Jul 22, 2019 4:39 pm

After the CORRECT nut has been fitted, you then fit the tab washer bending the two tags down into the two sprocket slots. This prevents the nut coming undone. The circlip fits in a groove round the nut, to stop the tag washer coming off.

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Re: G80 DYNAMO NUT

Postby Rupert123 » Mon Jul 22, 2019 8:15 pm

Thanks for your reply Rob, i have ordered all the bits off the club for the repair, also for some reason there was a hole drilled through the side of the nut just below the groove ??? who knows , in the club spares they also have a dynamo locating strip complete with two screws 010962 is this what stops the dynamo going in too far and is it a universal fit on all dynamos.
kind regards,
Martin.

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Re: G80 DYNAMO NUT

Postby Rob Harknett » Mon Jul 22, 2019 8:38 pm

Believe the dynamo strip hit against the engine plate as a stop. This strip may have elongated holes, so it can be set in the correct place, Cant remember. BUT, the important thing is the dynamo and engine sprocket MUST line up. You may not have the correct dynamo, it may not have the strip. That's not really a problem. Lining up the sprockets is the thing that matters. I thought the club was out of stock for the special nut and tab washer. The picture of the circlip is like a dudgeon pin circlip with two eyes to open it with circlip Plier's. Surclip was just a round wire like ring. Perhaps nuts were modified to take an STD flat circlip.

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Re: G80 DYNAMO NUT

Postby Rob Harknett » Mon Jul 22, 2019 9:11 pm

http://archives.jampot.dk/technical/Gen ... m_(Updated).pdf

Martin, Click the above link for pictures of what I have been talking about. eg Sprocket, Washer, nut, tab locking washer and its wire like circlip.
One part is not pictured, I also forgot it, that is the woodruff key. Half moon shape, sit's in the armature cut out, then locates in the sprocket slot to prevent the spocket turning on the armature shaft. The nut only tightens the sprocket on the tapered shaft. The key stops it turning on the shaft. Sometimes you may see a mag, 17 T sprocket used on the dynamo. The mag sprocket will not accept the key or nut locking parts.

The link did not work did it, guess you got an error message. I have fixed it. Try this link instead,
http://archives.jampot.dk/technical/Ele ... ynamos.pdf

Should anyone get an error message with a file in the archives. Send me the link and I'll fix it. Seems the file can be opened OK in the archives, when pasted in here it won't work. I don't know why this happens, or why my fix cures the problem, but it does.

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Re: G80 DYNAMO NUT

Postby Group Leader » Mon Jul 22, 2019 9:44 pm

Here are the nut, tab washer and circlip assembled. As was previously stated, the tab washer locks into the sprocket to prevent the nut coming undone. The circlip clips (awkwardly!) into the groove in the nut to stop the tab washer coming off. Make sure the circlip including its ends are truly seated in the groove. A lost nut and dynamo sprocket will make a very expensive mess!

Alan

Dynamo Nut.jpg
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1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:

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Re: G80 DYNAMO NUT

Postby Rob Harknett » Mon Jul 22, 2019 10:22 pm

Group Leader wrote:Here are the nut, tab washer and circlip assembled. As was previously stated, the tab washer locks into the sprocket to prevent the nut coming undone. The circlip clips (awkwardly!) into the groove in the nut to stop the tab washer coming off. Make sure the circlip including its ends are truly seated in the groove. A lost nut and dynamo sprocket will make a very expensive mess!

Alan

Dynamo Nut.jpg

As fragile as it seems, I have never had a circlip come off in some 60 + years. Just make sure the locking washer is good. when assembled, punch in the tabs at the end, so the washer stays flat. Your pic looks fine to me. You do not seem to have bowed the locking washer punching the tabs down. You should have no worries the circlip and washer will come off. I don't think the sprocket would come off, it may bend the dynamo armature and mangle up chains trying to do so.
what I have seen make a mess on some one else's bike is. One or more of the 3 screws holding the chain case onto the crank cases come undone. Those also should have a little locking washer I think you bend one bit on just one hex up a bit. Don't trust my memory thought. Last 3 screws I fitted was about 30 years ago, they have never come out since.

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Re: G80 DYNAMO NUT

Postby clive » Tue Jul 23, 2019 8:05 am

Cleaned threads then Locktite is probably better than those very small tabs for the chaincase to crankcase screws.
clive
if it ain't broke don't fix

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Re: G80 DYNAMO NUT

Postby Rob Harknett » Tue Jul 23, 2019 10:27 am

clive wrote:Cleaned threads then Locktite is probably better than those very small tabs for the chaincase to crankcase screws.

They are fiddly Clive and I have wondered how they manage to stay put. But so far they have. Never ever found one missing.

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Re: G80 DYNAMO NUT

Postby 56G80S » Tue Jul 23, 2019 4:03 pm

Last time I used those funny shaped tab washers for the rear part of the chaincase round the crankcase boss I used loctite as well as the tab washers.

Sad.

On topic, I always used to fit the locking washer and round wire spring clip on the dynamo sprocket nut. When I last had the dynamo refurbished, Tony Cooper advised me not to, just thoroughly clean and use loctite. As I had misplaced the spring clip I did as he suggested. OK so far but......................

Johnny B

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