Champion and NGK Spark Plugs
The right spark plug
The right spark plug for your Triumph is as important as any other part of your ignition system. As a general rule, Triumph 500 / 650 / 750 aluminum heads use a 14mm 3/4" reach plug. All Triumph iron heads use a 14mm 1/2" reach plug. Pre unit square barrel TR5 and 500 Grand Prix also use 1/2" Finding the correct heat range is up to the individual tuner.
Important note about heat ranges
Champion spark plugs heat range increases as the number gets higher
Champion (higher number=hotter plug)
NGK spark plugs heat range decreases as the number gets higher
NGK (higher number=colder plug)
Reading spark plugs can be challenging with lead free ethanol added gasoline. Please use caution with a major change or new engine and always use a fresh set of plugs when tuning for speed.
Spark plugs are sold in pairs or as a pack of four.