A secure dynamo mounting

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Greybeard
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A secure dynamo mounting

Post by Greybeard »

Has anyone come up with a way to improve the mickey mouse dynamo mounting dreamt up by AMC? Apart from being in the most ridiculously inaccessible location is there a way of being able to securely clamp it in the position it needs to be to tension the chain and make it stay there? :| The one on my 49 G80 seems determined to slacken its chain within a mile or two. I must confess that despite going to the expense of rebuilding the dynamo and fitting an electronic regulator I am very tempted to remove the chain altogether and simply rely on the battery for running the led lights and horn for the little they are needed.

Steve - AKA Frustrated of Yorkshire
56G80S
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Re: A secure dynamo mounting

Post by 56G80S »

My experience is that the adjustment, while fiddley, can work and remain in place.

I've found that there is a tendency for the chain to "tighten up" as the dynamo is locked in place. This leads to fun with loosening off again, leaving the chain on the slack side (1/4" whip is the correct setting and check for any tight spot first) and then it not doing the tighten up thing and being left with a loose chain! The bottom cross piece for the strap is often quite bowed because the upper bolt is overtightened.

Hope you took care aligning the dynamo sprocket with the engine sprocket and fitted the locating strip (although I know some don't fit the locating strip).

JohnnyB
Greybeard
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Re: A secure dynamo mounting

Post by Greybeard »

It does sound as if you have a similar experience to me, JB, but are more tolerant of the foibles :D I did wonder whether seating the dynamo on a thin rubber 'bed' or lining the securing band with rubber would help. Having just replaced the gearbox oil seal and fitted a larger gearbox sprocket, I'm not well disposed towards removing the entire primary drive yet again. I have previously found that removing the dynamo from the offside is impossible no matter how far I try to swing the gearbox back. Theres a lot to be said for my alternator G80 and the twins ;)

Steve
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clive
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Re: A secure dynamo mounting

Post by clive »

Steve a number of thoughts. If you cannot remove the dynamo without removing the primary you probably have the later type dynamo. The earlier one has a flat plastic end cap and when i had a 49 G80 could be pulled out from the offside, mind you i did not have the locating strip fitted and of course it required the timing side to come off which was a lot more trouble than the primary side!. I tend to start tightening the bracket with the chain looser than i want as the dynamo creeps round as you tighten. Perhaps a couple of goes and you should get it right.
I think the idea of putting rubber round the dynamo will not work as there is insufficient room. If you tried using tape i think it would only encourage creep as you did it up. I suspect your bracket may be bent as generally once the bolt has been tightened and then loosened to readjust it can be a pig to rotate the dynamo. By 49 the crankcase should have a scallop in it to clamp the dynamo against and the arms off the bracket should be a straight line not bent. I use a small spanner and tighten it well.
clive
if it ain't broke don't fix
Greybeard
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Re: A secure dynamo mounting

Post by Greybeard »

Thanks, Clive, I'll persevere. Im using the bike on a 100+mile run tomorrow so I will see how the current (ahem!) attempt works out. It does have an E3L fitted which complicates matters but I understand that a local VMCC section member has an E3 somewhere in his garage. If it shows up I'll give it a go, though as you say theyre never going to be easy to get at. Theres a lot to be said for using my bikes with carbide lamps - though it does take a while to light the stop lamp when its needed ;)

Steve
Andy G
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Re: A secure dynamo mounting

Post by Andy G »

Ref rubber seating, isn't the earth rather important? If you go this route, do ensure metal touches metal at some point.
Bombling contentedly around rural Aberdeenshire
Greybeard
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Re: A secure dynamo mounting

Post by Greybeard »

If it's sat on rubber there's still the metal securing strap so wouldn't be a problem, Andy.
Thanks. Steve
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