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A technical forum for all single cylinder Nortons

M50 Overbore


Greetings from Ireland.

I am in the process of rebuilding a 1962 Model 50. I am going down the route of the BSA A65 (+ 40 thou) piston and overboring the barrel to 76mm to give 399cc.

Has anyone ran this and if so what piston to cylinder wall clearance do you run?

I would also like to know does anyone have any technical data on these engines relating to specific engine measurements.

Right now I am looking for OEM barrel height, cylinder head thickness, conrod big end ID and crank big end OD.

38 ES 2 Piston ?


I think it's time for a re-bore on the 38 ES 2 motor

The only pistons I can find are  48 on.Nothing for the pre war Singles

I understand the GPM piston just needs the skirt trimmed a little, is this correct.

What are others using?




16h frame


hi i have straightened my 16h frame, aligned the wheels put a large level on both wheels vertically they look good now, but the bike still pulls slightly to the left, anyone got an idea why. pete

1933 International.


Could someone please confirm if a 1933 International should have a Dolls head gearbox or a Sturmy. I thought the Dolls head didn't come out until 1935. Seems a lot of pictures I've seen of 1933 models have a Dollshead. Many thanks.

Front brakes on Singles


Is the prewar one-piece front hub on the Inter steel and not cast iron? Is that why my Inter front brake is not as good as my 16H? If so, there's no solution that will make up the difference, is there? I'm hoping my new Ferodo shoes will bed in better but I can send the old ones off for better linings if there is no improvement.

AMAL Premier arrived...


Whilst I am familiar with Concentrics of yore, the Premier gives me some questions.  

Attached is pic taken from the lovely new color pamphlet that came with the Premier.

As per the this new color pamphlet, is the 2-piece brass/steel screw on LH (non-tickler) side of Premier now called the "Pilot Air Adjusting Screw"?  (pic attached).



I'm tired of poor brakes. Is the oval plate between the mounting pins one of the various ways to make them better? I don't even see how it fits because there is no room behind the retaining circlips on the pins.  RGM appear to sell them.

1953 ES2 dualseat


I'm restoring a 1953 ES2 and have a (BMS) copy of the 1950 Norton parts list, together with the supplements for 1951 - 1954. I can't find any mention of the dualseat introduced in 1953 (or even the 1954 dualseat). The dualseat fitted on the bike is mounted quite differently to that on a friend's 1957 19S.

We're wondering if the ES2's seat and its mounting points are original or a later modification / addition.

Can anyone advise?


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