Primary chain adjustment

[RodneyK]

I bought my 55 G9 as mostly a box of parts but the gearbox was already bolted into the frame so I didn’t pay much attention to it. After I got the rebuilt engine into the frame I went to test the primary chain adjustment mechanism and found that I had no travel in the gearbox at all. It was jammed in tight. When I removed a mounting bracket I could see that it hit the bracket at the front and the frame at the top rear. Is this the wrong gearbox for the frame? Wrong mounting bracket? Gearbox #MA12764G. Frame #016717.

[dave16mct]

Yes you should have a Burman B52 type. That's a later AMC box. By the way you should put the end cap of the swinging arm the other way round with the filler plug accessible from the oil tank side. You can't reach it otherwise once the primary chaincase is in place.
Dave.

[clive]

I guess it depends if you want to go down the correct box for the year (Burman GB box often called B 52 as they were introduced in 52) or stick with the AMC box which is generally considered to be better. You may be able to fit later engine plates but there are a number of issues to consider. Do you have the clutch basket, they are not easily interchangeable I think but happy to be corrected? The first photo appears to show the beginning of a crack in the mounting just above the 7 and 6. It may be a casting mark. The Burman box would have an adjuster on the outside of the engine plate, the AMC box had an adjuster in the middle. Your frame would not appear to allow that but the side adjuster might work ok.

[Groily]

I guess it depends if you want to go down the correct box for the year (Burman GB box often called B 52 as they were introduced in 52) or stick with the AMC box which is generally considered to be better. You may be able to fit later engine plates but there are a number of issues to consider. Do you have the clutch basket, they are not easily interchangeable I think but happy to be corrected? The first photo appears to show the beginning of a crack in the mounting just above the 7 and 6. It may be a casting mark. The Burman box would have an adjuster on the outside of the engine plate, the AMC box had an adjuster in the middle. Your frame would not appear to allow that but the side adjuster might work ok.

I guess the AMC box is 'generally considered to be better', and it's certainly tougher, but I have to say I very much like the B 52 box for its jewel-like operation, silent engagement of 1st gear at all times, and the supreme lightness of the Burman clutch that goes with.
While the spacing of the ratios is perhaps better on the AMC, with a higher 3rd (comparing my three AMCs to my one B52 anyway) the clutches can be heavy and - without wishing to say something heretical - I don't think three springs are enough. The best clutches I've had have had 4 or more, and there's just nothing as sweet as the Burman in my humble.
I've heard it argued that the Burman isn't really man-sized enough and there be those who prefer the more standard type camplate of the AMC compared to the barrel and plunger of the B52, but Ariel successfully used it on the Huntmaster 650s with a slightly longer mainshaft and dry clutch, and I thought the reason AJS/M swapped was only because Burman stopped operating, rather than in the search for 'more robust' or 'better'.

If you went for a Burman you'd probably get your money back or more on selling the AMC one, and it would, er, fit without mods or hassle. It is also what should be there and is definitely what I would try to do, for the square root of absolutely nothing that that's worth!

[RodneyK]

Thank you Dave, Clive and Grolly. You have all helped me before and now again.
My preference is to find a B52 box and trade or sell my AMC one but that may be difficult in my remote location. It appears that the only way to adapt the one I have is to grind 1/4” off the top of the casting to provide clearance for adjustment. That seems extreme. My clutch is just a pile of parts so I’m not even sure it will fit, let alone allow proper sprocket alignment.
Dave, thanks for the tip on the swing arm. I’ll fix that.
Clive, that is just a casting mark and the adjuster I have can only fit on the outside, presumably under the oil tank, but I have no clearance for the box to move.
Grolly, I’ll look for a B52 but might have to adapt what I have. Is there an easy way to check if I have the correct clutch parts?
I’m a bit frustrated by the mismatched parts but still hope to make it work. Your help is invaluable.

[Duncan]

Hi Rodney, it may be worth checking with the engine sprocket clutch and a chain in place you may not need to move the gearbox that far back in reality or maybe just a skim off the top of the gearbox would allow sufficient movement, it could be easier to replace the chain say every 5 years depending on use as it stretches than find another gearbox?

[RodneyK]

Hi Rodney, it may be worth checking with the engine sprocket clutch and a chain in place you may not need to move the gearbox that far back in reality or maybe just a skim off the top of the gearbox would allow sufficient movement, it could be easier to replace the chain say every 5 years depending on use as it stretches than find another gearbox?

Good idea Duncan, thank you.

[Groily]

Hi Rodney,
To see what the clutch bits should look like and what the individual parts are, the info in the Archives can be helpful even though the pictures aren't that brilliant. On a twin, there should be five plates, friction, and four plain so the basket has to take the full stack. Singles used a shallower clutch basket (fewer plates). The Burman has five studs, springs and cups, so that will tell straight away whether you have an AMC one or not, at least.
All versions of the AMC one are very different from the Burman - with a good few differences between early and later ones of those as well (another can of worms over which many of us will have scratched our heads over the years. I know I have).
See http://archives.jampot.dk/book/Owners_m ... Manual.pdf
http://archives.jampot.dk/book/Spares_l ... _twins.pdf
There are threads on here about using AMC clutches on Burman mainshafts and what it entails in terms of the clutch centre, alignment etc - but have never tried that myself. Can be done though.
Remote location won't help, I do get that - but I imagine quite a few things are going to have to be shipped your way as the beast progresses. Most 'stuff' can be got to most anywhere without too much hassle these days luckily. Best of luck!

[RodneyK]

Hi Rodney,
To see what the clutch bits should look like and what the individual parts are, the info in the Archives can be helpful even though the pictures aren't that brilliant. On a twin, there should be five plates, friction, and four plain so the basket has to take the full stack. Singles used a shallower clutch basket (fewer plates). The Burman has five studs, springs and cups, so that will tell straight away whether you have an AMC one or not, at least.
All versions of the AMC one are very different from the Burman - with a good few differences between early and later ones of those as well (another can of worms over which many of us will have scratched our heads over the years. I know I have).
See http://archives.jampot.dk/book/Owners_m ... Manual.pdf
http://archives.jampot.dk/book/Spares_l ... _twins.pdf
There are threads on here about using AMC clutches on Burman mainshafts and what it entails in terms of the clutch centre, alignment etc - but have never tried that myself. Can be done though.
Remote location won't help, I do get that - but I imagine quite a few things are going to have to be shipped your way as the beast progresses. Most 'stuff' can be got to most anywhere without too much hassle these days luckily. Best of luck!

So it appears that I have a Burman clutch, although I will have to get the studs, springs and cups form the club spares. With this in mind, it seems pointless to try to adapt the AMC gearbox. There is a fellow here in Canada who may be able to get me the B52 but if not, where else could I look? Will any Burman fit or do I have to look for specific numbers? So far, no one is interested in trading fo my AMC. Do you have a rough estimate of what they are worth? This is harder than I thought but I can do it with help from the forum. Thanks

[Groily]

I would think an advertisement online and in the Jampot would be a good start (to find and to sell/swap), and also contacting AMC Classic Spares and Russell Motors in case they have anything complete and usable. A lot of the parts are available from the Club and others, AMC Spares have been known to have shafts, pinions and other parts 2nd hand, but the shell and end cases may be harder. I think the earlier CP box would also go, but I don't know if there are any differences in the gearbox / engine plates there - someone here will know though, if they're a straight option. They were used earlier in the '50s on twins and singles and are also pretty good but with (another!) different 'spring box' gear selector mechanism.
Prices / values I'm not sure - but both ought to be about the same value I'd say at a guess - I think both are quite sought after. But it comes down, as ever, to 'willing buyer, willing seller' (and condition) when it comes to price. The AMC one probably has several applications in the Norton world as well as ours. The thing to try to ascertain with any Burman is that the mainshaft is the correct length for our bikes, not the longer version used by Ariel, otherwise that would have to be changed. As always, the difficulty (called 'human nature') is that whenever we try to sell something we're told 'nah, they're two a penny and no demand' and when we want to buy it's the sound of air hissing through teeth and 'rocking horse droppings mate'. But don't be discouraged!
There is quite a bit of data on Burman numbers etc on the web, but not sure how useful it is at the end of the day, as many of the bits are common.