Triumph Rocket 3 GT 2021 - Page 154

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Breakage
Breakage is usually caused by thermal expansion and thermal shock due to sudden
heating or cooling.
Normal Life
A worn spark plug not only wastes fuel but also strains the whole ignition system
because the expanded gap (due to erosion) requires higher voltages. Normal rates of
gap growth are:
0.00063 -0.000126 inches per 1000 miles (0.01 -0.02 mm per 1000 km).