Parts interchangeability

As a manufacturer, you need to keep costs down, so using the same part across your entire range of motorcycles makes huge commercial sense – rather than four different mudguards, why not one and fit it to four different models? While you’re at it, perhaps with internal mods and a different cylinder head, the same 500cc bottom end can power the commuter, sports and even TT models.

Famously, Norton used the same bore and stroke across its 500cc models for years, which certainly helped me out when restoring