Alternator rotor

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
BeenyBoy
Posts: 64
Joined: Wed Sep 18, 2019 11:42 am
Location: Lincolnshire UK

Alternator rotor

Post by BeenyBoy »

1965 csr

Hi guys-

I'm trying to refit the primary drive/clutch/alternator and find that when the rotor is pushed onto the mainshaft there isn't enough thread available on the end - pix attached.

There is a spacer which seems to fit between the main bearing and the drive sprocket and removing this gives me enough thread but the sprocket fouls the casing.

Any idea what I've done wrong ??
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Mick D
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Re: Alternator rotor

Post by Mick D »

Hi

I'm not too sure what the case is with a Wipac rotor but with a Lucas one has a recessed surface which is assembled outboard.

Does yours have a recessed face and if so does it fit if you reverse it?

Regards Mick
BeenyBoy
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Location: Lincolnshire UK

Re: Alternator rotor

Post by BeenyBoy »

Hi Mick

No both faces are the same- no recess
BeenyBoy
Posts: 64
Joined: Wed Sep 18, 2019 11:42 am
Location: Lincolnshire UK

Re: Alternator rotor

Post by BeenyBoy »

Yes- that's the strange thing- I'm sure that when I took it off the nut was flush with the end of the shaft- as you would expect. The drive sprocket is 'handed' putting on the other way round means the chain is touching the rotor- and anyway it makes no difference top the overall fitting as the inner face is flush against the spacer either way round.... a bit of a mystery....
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clanger9
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Re: Alternator rotor

Post by clanger9 »

There shouldn't be a spacer in there. Only enough shims so the chain "just" clears the inner casing.
This thread may help: http://www.jampot.com/forum/viewtopic.php?f=15&t=24488

Here's a diagram I made to show the correct arrangement, because it's not very clear in the workshop manual:
lightweight_main_bearings.png
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1989 Moto Morini Dart 350
1993 Ducati 750SS
BeenyBoy
Posts: 64
Joined: Wed Sep 18, 2019 11:42 am
Location: Lincolnshire UK

Re: Alternator rotor

Post by BeenyBoy »

Thanks clanger- that seems to make sense...although where has this spacer come from I wonder ?.... I haven't split the cases- just removed the primary drive so I could get the inner case off to clean it up and I put the crankshaft nut back on so I didn't loose it....so did I find a spacer and add it ?...don't remember doing so....mind you ..I can't remember what I had for tea yesterday...so that means very little.........strange though innit ?
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clanger9
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Re: Alternator rotor

Post by clanger9 »

It's a strange one. If you follow the threads above, you'll see there is mention of a spacer "041091" in the workshop manual, but this part isn't mentioned in any parts list.
It's not clear if/when it was fitted and to which bikes. Maybe it was only present on early models - possibly those that were fitted with two ball main bearings? No-one seems to know.

Regardless, mine is a very late CSR and definitely does not need this spacer. I'd be surprised if yours did.
1989 Moto Morini Dart 350
1993 Ducati 750SS
RL
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Re: Alternator rotor

Post by RL »

My experiance may help in that I have a 1967 rebuilt CSR that had a similar problem. I found that the sprocket had been fitted the wrong way round,ie sholder to the crankcase, should be as in the diagram previously posted. On fitting the sprocket the correct way round I found that I did need to fit a spacer/shim and then the rota and nut fitted okay.
RL
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Location: LINCOLNSHIRE UK

Re: Alternator rotor

Post by RL »

My experiance may help in that I have a 1967 rebuilt CSR that had a similar problem. I found that the sprocket had been fitted the wrong way round,ie sholder to the crankcase, should be as in the diagram previously posted. On fitting the sprocket the correct way round I found that I did need to fit a spacer/shim and then the rota and nut fitted okay.
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clanger9
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Re: Alternator rotor

Post by clanger9 »

It's certainly very easy to fit the sprocket the wrong way round. It somehow looks "wrong" when fitted correctly, so it's a common mistake. People then fit (or improvise) an unnecessary spacer to compensate.

The correct way is short shoulder innermost i.e. towards the crank. Long shoulder outermost i.e. towards the rotor. No spacer needed.
1989 Moto Morini Dart 350
1993 Ducati 750SS
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