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- May 7, 2005
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AMC-Norton modifications
AMC-Norton boxes, used on a wide variety of
models, sometimes suffer from layshaft bearing
wear. At one end of the layshaft is a ball bearing,
housed inside the shell. When this breaks up, the
layshaft flops about under load and rubs against the
adjacent output bearing; occasionally troubles ensue
in the kickstart mechanism when the bike is under
way.
Originally, Norton boxes had roller bearings in
this position, a much more satisfactory
arrangement. Due to a number of complaints,
Nortons eventually cottoned-on and recommended
replacement of the later ball races with roller
bearings of the old type.
If your AMC box is giving trouble, the re-
placement roller race is Norton part number
067710. A better (cheaper!) solution is to purchase it
from a bearing supplier. In this case the SKF
number is NJ203, or an equivalent FAG or R&M,
with a C3 (three dot) fit.
Page 116 The Vintage Motorcyclist Workshop
AMC-Norton boxes, used on a wide variety of
models, sometimes suffer from layshaft bearing
wear. At one end of the layshaft is a ball bearing,
housed inside the shell. When this breaks up, the
layshaft flops about under load and rubs against the
adjacent output bearing; occasionally troubles ensue
in the kickstart mechanism when the bike is under
way.
Originally, Norton boxes had roller bearings in
this position, a much more satisfactory
arrangement. Due to a number of complaints,
Nortons eventually cottoned-on and recommended
replacement of the later ball races with roller
bearings of the old type.
If your AMC box is giving trouble, the re-
placement roller race is Norton part number
067710. A better (cheaper!) solution is to purchase it
from a bearing supplier. In this case the SKF
number is NJ203, or an equivalent FAG or R&M,
with a C3 (three dot) fit.
Page 116 The Vintage Motorcyclist Workshop
