Sunday, August 8, 2010

Restoration Work---Carburetor Rebuild Part 1

If the cylinders are the heart of a motorcycle then one could consider the carburetor to be the lungs. As an anesthesiologist, I deal daily with cardiac and pulmonary function. I am fascinated by the lungs and so it is no surprise to me that I am fascinated with carburetors. Carburetors on classic bikes and their tuning are a never ending source of discussion and for many frustration. Been there and now I am going to divulge all I know. I plan to do this in several installations and while confined specifically to the carburetor on my bike many principles are transferrable to all makes.

Like any project, there needs to be a point of departure. In the case of my Model 7, I was interested in using the original carburetor which simplifies matters tremondously in that I was able to go to the original settings and tune from there. Others with more experience may want to upgrade or may not be able to find the appropriate carburetor at which point start with what you have.

Every carb initial setup by make for the period

Carb type confirmed

Initial settings on the bottom line

The carburetor on a 1951 Norton Model 7 is a Amal 76AK/1AT indicating what is conventionally described as a pre-monobloc carburetor, meaning that the float bowl is separate from the carburetor body. Often, Amal 76's will be replaced with 276's since the latter are generally more available.. These carbs are virtually identical and interchangeable down to the parts. The only difference between the two is that the 76 series carb has additional air holes at its base.

Float Bowl Side

Vent holes at base on an Amal 76

Along with the Amal publication mentioned above that includes a comprehensive parts list, here are a couple other references that are helpful in getting started:

Great book series by a real
authority on bikes

Amal Carb UK is a comprehensive site that lets you shop by original part number. Additionally, they have exploded diagrams of each carburetor type and you can select parts that way as well. Great site and great quality for a decent price. Definitely a rare combination!

Next post, we will tackle dismantling the carb, identifying potential faults, cleaning, and reassembly. In the meantime, if anybody needs info please drop me a line.


  1. Hey Chris,

    You 're right, Cylinder are the heart, for me during years i always thought that carburetor was the heart ... ok i've learn something today ;)

  2. The post is really knowledgeable. Thanks Chris, for searing.