UK no-sign up Motorcycle Home Mechanic Guide - Manual / Resource - Page 50
A feeler gauge can also be used to measure the gap but not on
Iridium or Platinum plugs as it is easy to damage the coated tip of the
centre electrode with the edge of the blade.
4 Select the correct gauge to match the specified gap and check that
it just slides between the electrodes with a slight amount of drag.
Most plugs come preset to the correct gap for the plug, and the bike
manufacturer’s specification should be the same, so it is rare that
a new plug needs to be adjusted. Conventional Nickel plugs can be
adjusted by bending the side electrode, preferably using the adjuster
that is fitted on a wire gauge, but Iridium and Platinum plugs should
not be adjusted.
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