[David_Hayward (RIP)]

The Carbtune is a a device to plug into the bellmouth of a carb such as my later father in law's Lotus Elan's twin 40mm Dell'Ortos. They assess airflow etc. and enables carbs to be balanced. Colourtune is used in place of a plug and shows a coloured light indicating ignition quality...too rich, too weak, or just about right. That way it takes account of an engine's age and you can set the timing manually to get the best for that engine. They are brilliant for bikes and you used to be able to get a 10mm adapator for Honda say heads.