tool for Horizontal gearbox level plug

Forums

Is there a suitable tool for the level plug on the Laydown / horizontal / Burman gearbox on early '50s Nortons?

It appears to be 1/4" square, but I tried the driver end of a 1/4" drive socket, which did not fit. The 4" adjustable spanner I fitted to it looked like just under 7mm when I measured it. So what will fit?

It would also be useful to find a nice tool to fit the square head of the tappets on my Model 88. Using a 4" adjustable is clumsy.

Paul

Likely to be 1/16 Whitwoth,…

Likely to be 1/16 Whitworth, which is 6.9mm across flats.

There were two types of…

There were two types of spanners for adjusting the tappets on the Norton twins, as one came in the factory supplied tool kit. I bought another type from Russel Motors, and it has the squared off end that fits onto the squared end of the tappet adjusters.

I always wondered...

... why they used the square rather than a hexagon? The previous owner of my ES2 fitted an Allen type screw which is much easier to deal with. By the way although Burman manufactured the gearbox (or at least the gears) it was a Norton design based on the old Sturmey Archer and essentially similar to the so-called AMC box fitted up till the last days of Norton.

What is the thread

on the level plug? I have an idea that an allen (socket head) grub screw might be a neat solution.

Otherwise, I may look for a 7mm open end spanner. A 7mm square socket would be nice....

Burman Norton boxes

I used to know a chap who ran a British bike shop in New Zealand in the late '70s and early '80s. He had acquired some tasty stuff. He had a pair of early AJS 7R magnesium Burman gearbox casings, which were empty. At some point he gave up trying to find gear sets for them, and sold them cheaply. The same buyer bought a brand new Manx Norton gear cluster. He was not pleased when he learned that the Norton gear cluster would go straight into the 7R casing.

I believe..

.. that later 7Rs used the so-called AMC box but no idea when they swapped over from the Burman. I've always found the Burman boxes as fitted to earlier Matchless and AJS to be clunky affairs.

early 7R box

is a Burman magnesium case for Norton gears - which were made by Burman for Norton. The Burman gearboxes for road bikes such as AJS / Matchless, Ariel, Vincent Comet are entirely different

early 7r gearbox

This is an early 7R Magnesium gearbox I overhauled some years ago. From memory it was nothing much like Norton and was similar but not the same as its road version. What I do remember are lots and lots of 1/4 rollers. I think it was 60 plus and not easy to keep all in place when assembling.

Barry Stickland

Attachments

IMG_0006.JPG

That's interesting...

... so although the box looks like an ordinary Burman it's not, being essentially Norton. Is the positive stop mechanism Norton or Burman?

gearbox development

It was a very long time ago that I saw these gearbox casings, probably mid or late '80s, and I could not give an accurate answer. I expect that this Burman race box used a Norton type cam plate and positive stop. It would be very interesting to have a look at one, because it might give clues to where the design for the laydown box positive stop and linkage came from. Is there any information on who designed this gearbox and where?

The doll's head...

... and other vertical boxes have positive stop arrangements very similar to the laydown (and indeed "AMC" box) with the only real design difference the external linkage on the earlier versions. As you say a view on the history would be interesting although I know nothing about this. I do know that the positive stop and selector mechanisms for roadgoing Burman boxes are entirely different

I've just popped mine out...

... and as I suspected it's a metric version - 10mm diameter, 0.9mm pitch (a bit odd?)

So not much help to you. To get a square drive, find a bit of mild steel tube that is a bit less ID than the diagonal dimension, heat it red and bash it around a bit of 7mm square scrap.

I did a simple calculation

if the square has 6.9mm sides, the total is 4 x 6.9 = 27.6mm

To get the internal diameter of a suitable tube, 27.6 / 3.1416 = 8.78

So, a tube of 9mm or 3/8" ( = 9.5mm) internal diameter will be about right. Just have to find some 7mm square bar....

On a different tack, I just found one of those cheap assembly spanners made from sheet steel about 1/8" thick, with an 8mm 12-point ring on one end. As yet, it does not go on the level plug square. I'm about to file the points of the ring a bit so they meet a square, and see if that works happily.