Champion N4C spark plugs must be fitted with the correct heat range to optimize efficient combustion and protect the engine from overheating. The Champion N4C is perhaps the most universally specified spark plug for the vintage British motorcycles from the 1960s and 1970s. The N4C has a comparable heat range to the NGK B7ES.This spark plug is appropriate for 1962-1972 BSA 500, 650, and 750 twins, as well as the B44 and B50 singles. Triumph specified this spark plug for many 500 and 650 twins from 1963-1973. May be suitable for other applications. This listing is for a single and multiple spark plug.
The Champion N4C spark plug has 14mm threads, thread reach of 19mm, a non-projected tip configuration, and a removable terminal for fitment with various spark plug cap types. Champion standard spark plugs have a copper core for improved conduction. The medium heat range may result in detonation in some machines that require a colder spark plug and may not be suitable for all vintage British motorcycles.
The spark plug fires the fuel mixture charge as it enters the combustion chamber, resulting in combustion and power. Spark plugs must be gapped correctly and free of heavy carbon and oil deposits to provide a strong spark.
The Champion N4C spark plug is threaded into the cylinder head and sealed with a special integrated crush washer. Refer to your workshop manual for the correct gap setting.
Please note: Due the nature of the product, we unfortunately do not accept returns on bearings, service tools or electrical components. Please be confident about your purchase before ordering. If you have questions, please contact us.
The product images shown are for illustrative purposes only and may not be an exact representation of the product received. Manufacturers occasionally make minor cosmetic changes to items, such as color, finish, label, or design. These changes do not impact the item’s function or compatibility. Please contact us if you have specific concerns regarding appearance.
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N4C Champion Spark Plug FAQs
Which Triumph and BSA motorcycles use the Champion N4C spark plug?
The Champion N4C spark plug was specified for many 1963–1973 Triumph 500 and 650 twins, and it fits 1962–1972 BSA 500, 650 and 750 twins as well as the B44 and B50 singles. It's one of the most common plugs for 1960s and 1970s British bikes. Always check your workshop manual before you fit it. You can also browse more Triumph electrical parts and BSA electrical parts.
What NGK plug is equivalent to the Champion N4C?
The Champion N4C has about the same heat range as the NGK B7ES. Both have a 14mm thread, a 19mm (3/4") reach and a non-projected tip. If your engine runs hot or detonates, you may need a colder plug, such as the Champion N3C or N2C. Riders who want a resistor-type NGK can look at the NGK BPR6ES. The NGK heat range guide explains how the numbers work.
What gap should I set on a Champion N4C for my Triumph or BSA?
Your bike's workshop manual gives the correct gap. On most Lucas points-ignition Triumph and BSA twins, it's usually about 0.020"–0.025". Check the gap with a wire-type feeler gauge before you install the plug. Also keep the plug free of heavy carbon and oil, so it gives a strong spark. Champion's spark plug technical resources cover gapping and how to read a plug. A magnetic spark plug socket set also makes removal and installation easier.
Is the Champion N4C the right heat range for my vintage British bike?
The N4C has a medium heat range and a copper core for better heat transfer. It suits most stock 500cc and 650cc engines. High-compression, modified or hard-ridden engines may need a colder plug to avoid detonation (pinging). Hotter plugs, like the Champion N5C, can help bikes that are mostly ridden around town and tend to foul plugs. Read the plug's color after a ride to check the heat range. You can compare options in the Spark Plugs & Leads section or call The Bonneville Shop for fitment help.
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