Gearbox Problems

Information relating to the Matchless G2 or AJS Model 14 250cc Lightweight
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Gearbox Problems

Postby IanAlexander » Wed Jan 20, 2021 10:31 am

I've just finished restoring a 1965 AJS CSR14 250cc and am suffering with a whining gearbox mainly in 3rd. I would really like to do something about it.

The teeth in the gearbox looked OK. I am wondering if I need to replace any gears or is there any other reason that would cause this?

Does anyone have a source for getting replacement gears?

I believe the later models had a close ratio box does anyone know what they should be? It could be that a previous owner has changed some of these from the original.

Be grateful for any help or advice anyone can give me.

Many thanks

Ian

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Re: Gearbox Problems

Postby SPRIDDLER » Wed Jan 20, 2021 1:27 pm

Welcome to the Forums, Ian.
Gear ratios for all 1965 models 14 are in the Owners Manual, page 5 (standard) and 6 (CSR) here:

http://archives.jampot.dk/book/Owners_m ... n_Book.pdf

Also see bottom of page 6 here:

http://archives.jampot.dk/book/Owners_m ... Manual.pdf
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Re: Gearbox Problems

Postby ajscomboman » Wed Jan 20, 2021 2:16 pm

Virtually near all L/W gearboxes whine in 3rd, it's a well known and common problem. My own used to and there isn't a fix as far as I'm aware. Jumping out off top and 1st is also another common trait but fixes for those issues is well documented.

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Re: Gearbox Problems

Postby clanger9 » Wed Jan 20, 2021 6:58 pm

"They all do that, sir."

How bad is it? I may have some spare gears here.

The CSR "close ratio" gearbox apparently has a different gear on the layshaft (043666 instead of 041290) which results in a different set of ratios. I can't confirm this, because I've never managed to find one...

Here is a link to an editable spreadsheet with all the part variations that I am aware of:
https://1drv.ms/x/s!AreW5w5WmJsqgR7NQGm ... l?e=oYqwHw

Please update if you find out anything is wrong or missing...
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Re: Gearbox Problems

Postby IanAlexander » Thu Jan 21, 2021 11:49 am

Noise is bad,have gearbox apart all gear teeth on layshaft gears look good just polished, teeth on main shaft gears 2nd & 3rd are a bit worn and pitted 1st & 4th look fine just polished,so I am wondering if a previous owner has replaced gears with pattern ones? And now they have worn?. Number of teeth on gears as follows 1st-main 16 lay 30 / 2nd-main 25 lay 21/ 3rd-main 21 lay 25 / 4th-main 28 lay 19. year of bike is 1966 so can anyone confirm if these ratios are correct. If they are and I'm not sure I will then address the noise problem Ian.
Last edited by IanAlexander on Thu Jan 21, 2021 12:17 pm, edited 1 time in total.

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Re: Gearbox Problems

Postby IanAlexander » Thu Jan 21, 2021 12:04 pm

Sorry my mistake miss count 21 teeth on main & lay not 19 Ian

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Re: Gearbox Problems

Postby clanger9 » Thu Jan 21, 2021 2:10 pm

If you have a 28/19 tooth pair on the 4th gear - then congratulations! You have the lesser-spotted CSR close ratio gearset.
Please could you post a photo of the 19 tooth gear? I've never seen one in the wild...

The other ratios are all correct (see the "Gear ratios" tab on the linked spreadsheet, above).

Maybe post photos of the 3rd gear set as well. Usually the gears don't wear that much - it's normally the layshaft bushes that go first.
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Re: Gearbox Problems

Postby IanAlexander » Sun Jan 24, 2021 1:48 pm

Thankyou for the info,looks like 2nd 3rd are common to all lightweight gearboxes,with 1st & 4th changed for the late bikes 1965 - 66 Photo of 19 tooth lay gear which is right for 1966 CSR.Photo of 2nd 3rd gears from layshaft, mating gears on main shaft are ok bushes are ok but it still makes a lot of noise? Do you still own a 250?
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Last edited by IanAlexander on Mon Jan 25, 2021 9:22 am, edited 1 time in total.

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Re: Gearbox Problems

Postby clanger9 » Sun Jan 24, 2021 5:48 pm

Thanks! I often wondered how they'd managed to get an 19 tooth gear in the same space as an 18. Thinner teeth, apparently...
It's hard to tell from your photo, but those gears don't look especially good. Here are two spares set from my parts box (which are also a bit ropey):
IMG_0362.jpg


I don't have my 250 any more (sadly) - it was was sold las year to make space for another project.
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Re: Gearbox Problems

Postby Stan Palmer » Sun Jan 24, 2021 5:59 pm

The change of just one tooth on the close ratio gear is intriguing. The PCD of the gear on lay shaft and mainshaft must roll on each other, so the mating gear would also have to be changed, and both would employ a slightly narrower tooth pitch. The Tiger Cub always uses a tooth less on the mainshaft when there is a tooth more on the lay shaft, which presumably means they can use the same cutter throughout. It means the sum of teeth on a pair of gears is always the same. On the example given above the totals are 46 for all gears except the 19 and 28 pair. Just puzzled as I normally find different companies employed the same basic principles because of the movement of staff.
Stan

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