650cc alternator twin primary drive set up

Information relating to the Matchless G12 or AJS Model 31 650cc twin
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jim griff
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650cc alternator twin primary drive set up

Post by jim griff »

Hi All,

I have query regarding the AMC alternator primary drive set up. I'm in the process of finishing my 63 CSR and cannot fathom the order of the build sequence for the front sprocket / rotor / distance piece. I cannot find any schematic drawing of this anywhere, does such an exploded drawing exist?

The crank mounted drive sprocket has a manufactured shouldered distance piece on one face that I assume fits towards the bearing, holding the inner chainguard wormed race in situ. The Rotor I assume butts up to this folllowed by another distance piece of 1/4" washer under the pressure release nut, or does said distance piece washer go between the drive sprocket & rotor? What is the countersunk face for? It's a perfect fit into the outer rotor, so do I assume it's simply for this?

Additionally The previous owner must have had problems with the chain distance / offset, as the outer primary case and alternator as both have witness marks where the chain has rubbed in the past!

Any help will be greatly recieved to what order the parts are fitted
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Duncan
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Re: 650cc alternator twin primary drive set up

Post by Duncan »

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bjork
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Re: 650cc alternator twin primary drive set up

Post by bjork »

As shown by the upside down (Australia issue) drawing above, the sprocket fits with the shoulder facing outwards. The sprocket sits tight up against the oil scroll spacer, which is tight up to the bearing inner race. The distance piece will probably have witness marks on it to show how it was assembled previously, but as you guessed it goes with the chamfer fitting in the alternator rotor. My own 650 came to me with this all arse about face and similar marks all over the inside of the cases. Mainly due to loose/worn chains flapping about. Also if you get it wrong the sprockets will be a long way out of line from each other. I checked it ;)
Using yesterdays technology to create tomorrows problems today
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ajscomboman
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Re: 650cc alternator twin primary drive set up

Post by ajscomboman »

Sprocket shoulder out wards, domed spacer, rotor domed face inward, locking tab washer and then breather nut. If you reverse the dome and rotor the locking tab washer doesn't do its job.
jim griff
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Re: 650cc alternator twin primary drive set up

Post by jim griff »

Thanks all,

That all makes perfect sense now. The struggle is now over and I can finish the job ready for the good? weather

Jim
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Malleon
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Re: 650cc alternator twin primary drive set up

Post by Malleon »

jim griff wrote:Thanks all,

That all makes perfect sense now. The struggle is now over and I can finish the job ready for the good? weather

Jim
Seeing is believing, Jim lad!

I've been waiting a long time for the promised trial run on it. I will now hold my breath !
jim griff
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Re: 650cc alternator twin primary drive set up

Post by jim griff »

Ha, well good things do come to those that wait!
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