1928 3 speed
before I go off on the search for 18mm plugs (I dont use plug caps so no clearance problems) I am sure someone has tried an adaptor and 14mm plugs I was wondering about some that are said to be compatable with ‘modern’ two strokes, Is there any information around? short reach or long reach and make and type. Perhaps someone has been really naughty and used 10mm! 😉
I fitted 18mm to 14mm adaptors to my 1932 Flyer for two reasons, I could only get 18 mm plugs in short reach. The head requires long reach so as not to shroud the plugs and there is a much bigger range of plugs in 14 mm. You must check the length of thread in the head before fitting long reach plugs as if any thread extend into the combustion chamber it will carbon up and damage the head threads upon plug removal. I never have any plug problems. I used to fit equivalent to NSK 6 but now use 5’s.
I have also fitted extended nose plugs as I have plenty of clearance between head and piston.
18mm long reach plugs ARE available. At the behest of the Bugatti Owners Club, Tim Green (The Green Spark Plug company) acquired the tooling for the KLG ML50 plug from the remains of Smiths Industries, who had bought the KLG rights in the late 1920s from Kenelm Lee Guinness, who committed suicide in 1937, aged 49. These brand new KLG ML50 plugs are the equivalent of the Lodge CB3 and Champion 7COML, so are well-suited to the needs of the Scott. When I last bought some, about a year ago, they were £8-50 each.