Gear change 48 Matchless G80

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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areg
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Gear change 48 Matchless G80

Post by areg »

I am not new to motorcycles, but the Matchless if the first bike I have that is pre 1980's.

I am new to the bike having just bought it,but have come accross a situation that I am not too sure if it is the way it should be.

Shifting through gears I have a neutral beween each gear. The behavior is not like false neutrals you get on more modern bikes.

It is very consistant. Changing from 1st to second I have to press down the gear lever twice. It works exactly like first shif neutral second shift 2nd, and it fillows in the same pattern for the rest i.e. 2nd to third first shift neutral second shif 3rd and so forth for the 4th.

I do not need to lert go of the clutch, just a double move. The action is so consistant the seems as if that is the correct way.

Is there anything wrong or that is how it should be.

Thanks for your feedbacks
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Biscuit
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Gear change 48 Matchless G80

Post by Biscuit »

Definitely wrong! Firstly check that the gear lever is not being obstructed from full movement, ie the exhaust pipe, if this is ok, remove the kickstarter case, you will see a quadrant, operated by the spring box and pawls, this meshes with a small pinion on the end of the selector shaft, both items are stamped with a small'o', which should coincide. If this is ok you will have to go deeper, possibly worn selector forks. I'm assuming you have the relevant manuals, if not do not attempt this until the information is at hand. The Spares Scheme supply manuals, or look here http://217.157.196.176:8181/ajs/Edited by - Biscuit on 21 Aug 2006 11:28:10 AM



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areg
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Gear change 48 Matchless G80

Post by areg »

Biscuit, thank you for the valuable information. It appears that the correct box is the Burman CP G45.

The problem (as fun as it is) is not restricted pedal movement touching something else. So will have to dig further.

I am running 30W oil in the box but it appears that I can replace that with more modern gear oil.

The other issue I have to take care of is a leak from the kickstarter shaft. I am hoping there is a seal or an o-ring of some kind.
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itma
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Gear change 48 Matchless G80

Post by itma »

No wonder you have problems, who on earth put 30w in a gearbox?
these boxes were designed to run on a grease/oil mixture, and there are no oil seals in it to speak of.
If you are lucky,underneath you will find a drain plug; not all boxes had them; if not you will need to remove the outer cover, and stuff grease in with a grease gun, the amount is not critical, about half a pound, them add a cupful of 50w. I also like to chuck in some colloidal graphite powder from time to time. There is availiable a semi-fluid grease, but I have no experience of it.
The kickstart shaft always has a weep, more so if its its Knackered by the 30w,
cut a felt washer and squeeze it between the kickstart pedal and the case.
Any excess oil/grease will find its way out via the high gear bearing, and settle down to the corect level
These gearboxes are bullet proof, but are famously slow changeing, try using a firmer foot pressure,and don`t try to drive it like a modern bike.
Welcome to the world of old bikes, which is a matter of mindset as much as anything else,congratulations on choosing a sensible bike
Don Madden
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Gear change 48 Matchless G80

Post by Don Madden »

Hi, Areg. Are you sure of the model year of your bike? In the 1948 year they started fitting an oil seal to the high gear bushing, behind the drive sprocket, but the G45 stamped into the box indicates being manufactured in 1945 & likely fitted in 1946.

In any case, Ken's, (ITMA), suggestions are spot on.

Obviously, the box is quite old & corrosion or breakage of the shifting parts could also be a factor. I suggest you follow the advice & at least remove the outer cover for a look.

Use proper British Standard tools as SAE & Metric are just enough similar to damage the hardware, which you cannot find at the local Do-It Center.

I have a 1947 G80 project bike & some dismantled gearboxes if you need a look at the innards before taking it on.

I also live not far away, about 50 miles & away & have some experience with these.

Cheers, Don.

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areg
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Gear change 48 Matchless G80

Post by areg »

LOL, itma the answer to the first question is I did, per specifications in the owners manual both for 1948 AJS and Matchless page 13, quote Gearbox Lubrication: Engine oil, and then page 3 gives the amount 30 fl oz. On both books the original amount of 1 lb 14 oz has been crossed off.

The positive aspect is that there is a drain plug and the bike was not driven for more than 2 easy miles with 30W in the gearbox.

So I am still alittle confused logic tells me 30W for a gearbox is too thin, but have seen funnier things in my life.

On another note the book also refers to using engine oil in the primary chain case. Now how come the clutch plates do not get splashed with oil that must be flying around?

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itma
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Gear change 48 Matchless G80

Post by itma »

re the clutch plates, if you search back through the gibberish, cats and legpulling of recent posts, you`ll find that subject covered at needlessly long length
Never seem a mention of 30w oil in the gearbox anywhere in any book.
remeber the engine oil of 1948 bears little resemblance to oils of today, in your chaincase 30w is ideal, you can use auto transmission oil also, some will aver to the contrary;
the trick is to only use sufficient to touch the bottom run of the chain.

]
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areg
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Gear change 48 Matchless G80

Post by areg »

Thanks guys, I took the gearbox number based on a list of production dates on a list I found here:

I will try to locate the one on the bike but the numbers for 1948 appear to be:

G45B48
G45D48
G45F48

I assumed G45 was the version B stood for Feb, D April, & F June and finally 48 the year.
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itma
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Gear change 48 Matchless G80

Post by itma »

If you don`t already have a cat you may find it helpful to get one for future posts
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areg
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Gear change 48 Matchless G80

Post by areg »

Itma, is that cat as cats and dogs? :) Anyway the actual number on the box is G45M47, whihc probably implies 48 model year produced in 47. So grease seems to be the answer. Probably synthetic as I do not have to worry about seals.

I will take the front cover off and see if I can make some head or tail out of it
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