Vespa - Which Spark Plug Should I Use Guide

There are two basic types used on classic Italian scooters. The main difference between the two types is the reach of the threaded section into the gebustion chamber. If you use the wrong plug you could cause serious damage to the engine. (A good rule of thumb is older scooters pre rally use B#HS-short, later model scooters and Lambrettas use B#ES-long plugs.)To de-code a NGK plug look below:B: Indicates 14mm thread diameter in the cylinder head. This diameter is used on all Vespas