A modified motorbike is typically considered a standard model that’s undergone some modifications to change its performance or style, or for practical reasons. A custom bike is specifically built to be unique, using a mixture of parts to create a bespoke machine. Popular custom motorbikes are those factory-built to look like models from the 1960s or 70s. While standard insurance may be enough for a modified bike, you may need to search for specialist custom motorcycle insurance for a bespoke model.