AJS & Matchless Owners Club

Hi to all, my first post here on this wonderful forum.
Am in the process of doing up a 53 M20.
The gearbox mainshaft is not all that straight anymore, so I plundered another "B52" I had lying around.
The box in the bike has number GB2AB53, the donor one has GB1AA53 (for what it is worth after all these years..).
When comparing all the bits, it appeared that the sleeve gear in the donor box is longer by 2,8 mm.
The difference is in the length of the teeth part.
The front edge of the teeth part is also more chamfered.
In the spare parts list for 53, the part nr. in the text is G-6-2, in the drawing it is G-6-5 / G-6-2.
For later years it is G-6-2 in the text, in the drawing it is G-6-5 / G-6-2.
Anyone who has a clue on this?

Another thing, one of the selector had a pegged fork, the other selector was welded up, as in 1955 onwards.
I take it they are interchangeable?

Cheers, Bennie

I do believe the donor box GB1 is for a 350. GB2 for 500. So you may consider, the donor box is not much good except for any parts that may be identical to the GB2 500 box.

As far as I am aware, there is no difference between a 350 and a 500 B52 gearbox. Internally they are the same. I have a sleeve gear out at the moment, if you could measure the overall length of your two samples I can compare the dimensions with mine, Bennie.
I also have a close ratio B52 gearset and the sleeve gear there appears shorter but it is only the width of the toothed portion which differs, the overall length is the same. To eliminate this unlikely possibility from the discussion, count the no. of teeth on the sleeve gear. Standard is 28 teeth, close ratio is 25 teeth with a correspondingly bigger layshaft 4th gear.
The B52/GB box was made for use in other machines eg. Ariel and it's also possible that you have a stray gear from another variety of B52.
The two types of gear selector fork/rod are interchangeable but usually both are of the same type in any one gearbox!

Rob, yes, the GB1 probably is of a 350 according to a list I saw compiled by an USA owner.

Zwarts, the overall length of the GB2 one is 72,7 mm and for the donor it is 75,5 mm.
Both have 28 teeth.

Here a picture of the 2 gears side by side, with the rear side of the teeth in one line.

My standard Matchless Burman GB/B52 sleeve gear (28 teeth) is 72.7mm overall length, as your original.
Interesting to compare the two in your photo - but I cannot say what is from or intended for. There appear to be many differences in these Burman boxes, some minor and others less so. There's also a lack of reliable documented evidence to help identify parts.
Our parts books often give alternative part nos. on the diagrams for many of the items but then only one variant is listed. Sorry I can't be of more help Bennie.

Thank you, zwarts.

Only now I see I made a mistake in the part numbers I mentioned earlier for the drawing numbers for the later models.
It is not G-6-5 / G-6-2 but G-6-8 / G-6-2.
The G-6-5 and the G-6-8 designation could be for the gear without bushes, and G-6-2 with bushes included (as it says in the text).

Also, the number for the mainshaft second gear, the one that slides into the sleeve gear, changes in the drawing over the years.
For 1953 it is G-10-4 / G-10-2, for 1954/55/56 it is G-10-5 / G-10-2.
However, the 2 second gears I have appear identical.
But this observation is not conclusive enough to say that the different numbers mean identical gears.

As you can see in the picture, there are no scoring marks on the edge of the sleeve gear.
The layshaft second gear is sufficiently free from it.

Bennie, PM sent which may help. Andy