1954 model 18 ajs clutch jumping/snatching

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
Mick D
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by Mick D »

Hi

Not sure if you replaced the five clutch springs: if not, have they lost tension - if so were the replacements the correct length?

It sounds like the springs are not exerting enough pressure on the clutch, have you tried increasing the tension?

Regards Mick
neil cairns
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by neil cairns »

If you look there is a question by me about clutch cable part numbers. My '53 18S combination clutch was getting very stiff, and sometimes the clutch would stick them engage sharply. I put this down to a worn cable. BUT a new one did not improve it. So I purchased a nylon lined cable kit from Venhill ( BRI-1-100, classic British Clutch Cable Kit). It is a much beafier cable and only took 35 minutes to cut to size and soler the nipple on. I now have a super-smooth clutch lever action and no more Kangaroo leaps!! ( < www.venhill.co.uk >)
SPRIDDLER
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by SPRIDDLER »

Hmm, well that's a two-brew headscratcher. :? You've evidently been very thorough and it all looks very standard.

When enlarging your photo the clutch basket does look rather 'over-full' with plates. I just wonder if it's the shallower 350 basket which has two fewer plates than the 500 clutch. Perhaps when the clutch is freed the first steel plate is moving out beyond the basket and then catching or 'hanging up' when the clutch is re-engaged.
Perhaps the new corks are holding the plates further apart and the set of plates is taking up more space in the basket than worn corks........
Here's a photo from a tech article which shows the plates inset further/deeper into the basket:
Clutch B52.JPG
It's from this article on a B52 clutch rebuild which may at the least trigger some more thoughts:
http://archives.jampot.dk/technical/Tra ... ebuild.pdf

As a very daft thought :roll: I suppose the 'kangarooing' isn't the engine cutting in and out.................... :rofl:
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clive
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by clive »

I would agree with Spriddler that the clutch basket looks full. I wonder if on hard acceleration the outermost friction plate is slipping beyond the end of the outer basket. It would then stop the clutch going fully home and make a harsh noise as the basket rotated behind it. If it slipped back into place you would then see no problem on dismantalling the clutch. I have had this problem in the past when fitting all new clutch friction plates. There were thick and thin plain plates (from different suppliers or originally different years not sure) and if you have the thicker ones plus plus new friction plates it may be all too deep. I got round it by fitting 4 new and one old friction plate. Another possibility is that you have an original type very thick plate fitted as the first plain plate. These were only fitted to the 350 and could be replaced by a plain plate. Again this would help.
clive
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JimFitz
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by JimFitz »

Sprid suggested that the weaker 350 shock absorber spring may have been fitted. I have looked at your replies and I cannot see whether you have checked - worth a look.
What I would do at this stage is run it up the road without the outer chain case fitted until you get the problem then you could see straight away whether the outer clutch plate is hanging clear of the basket or the shock absorber slipping.

Jim
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Pharisee
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by Pharisee »

The previous owner / restorer(?) had seem fit to install a 'mongrel' clutch on my '55 M18S. The drum was deep enough for a '5 plate' clutch but the centre hub is the shorter '4 plate' item as fitted to the M16. The 5 spring bolts are the long 2" items and the push rod is also a longer 10.3/16" item. There are only 4 friction plates and 5 steel plates instead of the 5 and 6 that should be fitted to a 500. Having said that, it workes well and there is no slipping under load. I will, at some point, find a longer clutch centre hub and fit the missing pair of plates.
18S_2260-small.jpg
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SPRIDDLER
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by SPRIDDLER »

Pharisee wrote:..on mine.... There are only 4 friction plates and 5 steel plates instead of the 5 and 6 that should be fitted to a 500. Having said that, it workes well and there is no slipping under load.
JimFitz wrote:What I would do at this stage is run it up the road without the outer chain case fitted until you get the problem then you could see straight away whether the outer clutch plate is hanging clear of the basket or the shock absorber slipping.
Yep, and while the outer chaincase is off maybe take out one plain and one friction plate (making it as a 350 clutch would be) and run it up the road (with trousers tucked well into your boots ;) ). It might slip a bit (might not), but if it doesn't snatch or kangaroo.......... :beer: .
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Andy51
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by Andy51 »

The outer clutch basket is, I believe, common to both 350s and 500s; the inner clutch centre is shorter for the 350. Removing a friction and plain plate is certainly worth trying, it will at least eliminate one possible source of trouble. Andy
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AJS 500
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by AJS 500 »

SPRIDDLER wrote:I'm assuming you have the standard B52 'box and 5 spring clutch.
Evidently the problem only exists (or is only noticeable) under high load.
Was this problem occurring before you o/hauled the clutch with new parts?
Does the snatching occur whilst the clutch h/bar lever is being eased out or after it is fully released?
I'm a little surprised that you have needed to (or were able to) fit a spacer to increase the shock absorber pressure since from memory (poor) it's quite a job to get the nut started as it is, never mind with an additional spacer. Obviously you have fitted the dished cap between the nut and spring :? The 500 has a stronger s/absorber spring than the 350's. Could yours have a 350 spring?

Various random thoughts......
Primary chain snagging on the dynamo chain? (Recipe for a real disaster!).
Do the new friction plates have individual 'corks' or a continuous bonded lining? If bonded, maybe part of a lining is unstuck.
Are the 24 clutch rollers the correct ones? From memory they are fractionally shorter than 'standard' 1/4" rollers.
Clutch basket nut not really tight?
If the primary chain is badly stretched perhaps when under high load the links are not engaging cleanly with the engine or clutch sprocket teeth. (Long shot!)
Is the actuating mechanism at the r/h side of the 'box (3 balls, a fixed and moving plate) correctly assembled?
Does the clutch release pushrod move freely and is not rusted/gummed up/bent?
Are the 5 new clutch springs free to move in their cups and not binding under high load when the clutch is being engaged?

(Must stop wittering now and decant the Claret for dinner............. ;) )

After dinner thought...........
You don't say what other work you have done but is the spacer 010629 in place?
Drive axle spacer '54.JPG
Turned out it was the clutch rollers being the wrong length. Purchased the bike from my uncle who has built many AMC bikes over the years and is a good engineer so I trusted they would be right ones. I think when I built the rollers up using smears of grease it masked the basket wobble. After measuring and replacing with the slightly shorter ones( admittedly easy to overlook due to the similarity in size) all problems solved.
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AJS 500
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Re: 1954 model 18 ajs clutch jumping/snatching

Post by AJS 500 »

Andy51 wrote:The outer clutch basket is, I believe, common to both 350s and 500s; the inner clutch centre is shorter for the 350. Removing a friction and plain plate is certainly worth trying, it will at least eliminate one possible source of trouble. Andy
Inner size is different, NOT a 350 clutch fitted. I found the new bonded friction plates are thicker than the original corks so I removed one. Clutch works fine now I've changed to rollers to the correct size.

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