Lightweight swingarm jaws opening out

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Lightweight swingarm jaws opening out

Postby Roderick » Wed Mar 11, 2020 5:25 pm

I recovered a beaten up LWT 250 Model G2 from a landfill site many moon ago thinking it might be a useful spares source someday. I was about to use the swing arms off it in the current restoration of another AMC 250 but have just noticed that the jaws that hold the the rear wheel spindle, measure about 1/16 inch.wider gap at the rear than at the front. It's plain to see from a side view that the jaws have opened out. Is this a common fault to look out for on the Lightweight swing arm or is mine just the case of a particularly, badly, abused example?

Rod

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Re: Lightweight swingarm jaws opening out

Postby cbranni » Thu Mar 12, 2020 9:09 am

Seeing that you have no replies I shall say that a 1/16" is nothing to worry about, you could clamp it up in a vice and give it a squeeze.

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Re: Lightweight swingarm jaws opening out

Postby SPRIDDLER » Thu Mar 12, 2020 1:41 pm

I agree with Colin and I'm not sure I would be able to 'plainly see' such a tiny (1/16") difference. It could've been like that from new.
I'm not familiar with L/W's and may have misunderstood the issue, but surely the 'spread' in the s/arm jaws will close up anyway when the wheel nuts are fully tightened?
EDIT.
Hmm, maybe you mean the 'slot' for the spindle each side of the end of the swing arm opens up by 1/16" over its length?
Here: (Not a L/W swing arm.)

Wheel spindle slots.JPG
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Re: Lightweight swingarm jaws opening out

Postby Roderick » Thu Mar 12, 2020 3:00 pm

Yes, I'm talking about the slot for the spindle.

On the British bikes I'm used to, like the AMC Heavyweights, this is usually a lovely cast bracket brazed onto the arm tube. In this case it looks instead like it has been formed by pressing the end of the swingarm tube flat & machining out the slot. Cheaper but can't be as strong as the Heavyweight jaw/slot & looks like it might be prone to distorsion if abused. Then again maybe quality control when it was made is the explanation & that's the way they left the factory. I hadn't another similar to hand to compare it with to check.

I was about to spend money on replacing the swingarm spindle on it but hesitated when on cleaning it I noticed that the jaws opened out and now I am wondering if I should try to find another.

Rod

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Re: Lightweight swingarm jaws opening out

Postby Mick D » Thu Mar 12, 2020 3:18 pm

Hi

I have no direct experience of lightweights but I'd be very surprised if your swinging arm is unusable.

A 1/16" taper would ease installation of the spindle so may actually be by design.

The only way I can imagine to distort your forks would be to try and fit a larger diameter spindle with considerable force - is your current spindle per design?

From memory the swinging arm forks on both my AMC HW and Triumph have a slight taper.

Regards Mick

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Re: Lightweight swingarm jaws opening out

Postby Martin.S » Thu Mar 12, 2020 8:08 pm

Mine were tapered - I thought that wasn't right so I welded them up and filed them to size - perhaps they were supposed to be like that?

G5 Swinging Arm.jpg


Here they are before I welded them.
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Re: Lightweight swingarm jaws opening out

Postby clanger9 » Thu Mar 12, 2020 8:56 pm

I suspect they're all like that. I just checked my spare swingarm and it's 1mm wider at the end of the fork.
IMG_1308.jpg
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Re: Lightweight swingarm jaws opening out

Postby Roderick » Tue Mar 17, 2020 12:02 pm

It may well be the result of past, brutal over-tightening of the rear wheel spindle nut on the Lightweight pressed steel swing arm which is softer than the cast or forged bracket on the AMC Heavyweights. I am not saying it's impossible the widening has been there from the beginning but I have not myself come across a case of jaws opening slightly to aid spindle assembly on any other make of old Brit bike I've dealt with and that's not a few. The one I know were always parallel as you might reasonably expect. I notice one of the jaws on one of these swing arms is also bent slightly slightly sidewise too. I can't imagine that on a Heavyweight.

I will try straightening & then increasing the diameter of the adjacent washer.spacers when assembling the spindle/wheel into the swingarm assembly.

Rod

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