Side view of gearbox
The next part I wanted to have a look at was the gearbox. From the owners club forum I understood that there should be a gearbox number stamped somewhere on the case, in addition to the engine and frame numbers (the gearbox and engine are separate units on these bikes). However with the years of accumulated crud and grime I hadn’t yet spotted this so needed to take a closer look.
After a quick wipe with an oily rag, sure enough the numbers were revealed – G3B51 and 169. Now I’m guessing that the 169 is the serial number of the box, but what does the other code mean? My thoughts were that the 51 related to the year (1951) which fits with the engine number, and that the G3 is because it is fitted to a G3Ls model bike. But what was the “B” in the middle? Further trawling of the forums was required.
The gearbox number stamp
Most information that I was able to find related to the Burman “B52” type gearbox, apparently so called because it was introduced in 1952. But if my bike was made in 1951 then it would pre-date the “B52” gearbox by a year and so must be something else. Perhaps it’s a “B51” gearbox I thought, but various searches found no mention of such a beast.
Finally someone on the owners club forum kindly provided the answer. This type of gearbox was indeed made by Burman and is referred to as a “CP” type, although I’m still trying to work out exactly what “CP” stands for, if anything. Anyway, one more step closer to knowing exactly what it is that I am the proud new owner of!
The keen-eyed amongst you will also have spotted one further small issue with the bike that I hadn’t spotted previously in the above photo. It seems that the lick-start lever has been welded onto the shaft, presumably because the splines had worn away causing it to slip. But the mechanic already had a spare shaft in his workshop so thankfully no real problem there, assuming of course that they could get the old one out of the box first!
Dear Mr. James,
do you know what gear oil do i need to my 1963 G3
Hi Yaniv,
Sounds like you should join the AJS and Matchless Owners Club! Have a search on the G3 forum here and you’ll find the answer to every possible question you could ever think of regarding your bike.
I run my gearbox on a mixture of thick oil and grease as anything quickly leaks out through the non-existent ‘seals’. However, your gearbox on your 1963 model will be a later type to mine and will therefore have a better sealing system. The original owners manual (see here) specifies SAE50 oil for both gearbox and engine so that will be a good start. Just make sure you don’t use modern multi-grade oil (e.g. SAE20-50) which will be too thin or oil with detergent in which will loosen up all those lumps of crud which are loitering in your engine (the filter system probably won’t cope with removing them).
Hope this help, happy riding!
James
thanks for making it a little clearer regarding what box relates to a 51/52 g3 it a minefield on changing parts b52 or cp. thanks
Thanks David,
One other note I have recently discovered about these gearboxes: the clutch type was changed in the CP gearbox in 1951 to the type which was used in the Burman (B52) gearbox from 1952 onwards. So in ’51 gearboxes you get a pre-51 CP box but with the later post-52 Burman clutch. Must have been one of those changeover periods.
Just to add to the complications and confusion hey!
James 🙂