Hello Does anyone know what sparkplug fits the Bonneville 750 Harris from 1986? In the internet I find several ideas: some say NGK B6 others B8. The motor seems to be original. Thank you. Romeo
A search gave me the info below. When I changed the plugs on my 25 year old Ducati I went for NGK iridium versions on the basis that I don’t do many miles on the machine and will probably never change them again so go for the best. The standard spark plug for a Harris 750cc Bonneville (based on the Triumph T140V) is the NGK B8ES. However, depending on the specific model year and usage, other options like the NGK BR8EIX (Iridium) or NGK B9ES (for hard use) may be suitable. The key specifications for the standard B8ES plug are a 14mm thread diameter, 19mm thread length, 20.8mm (or 21mm) spanner size, and a 1.0mm spark position. Standard specification (NGK B8ES) Spark Plug Type: NGK B8ES Thread Diameter: 14 mm Thread Length: 19 mm Spanner Size: 20.8 mm (21 mm) Spark Position: 1 mm Spark Gap: 0.5 mm Alternative/Upgrade options NGK BR8EIX: An iridium-tipped plug for improved performance. It's often a long reach type. NGK B9ES: A "colder" plug often recommended for hard-use conditions. Champion: Some models may also use Champion alternatives, such as the Champion N5C for the T140V.
