When is a Norton not a Norton...? The pics above were sent by Marcin in Poland and the engine bears a remarkable similarity to vintage Norton design but clearly it isn't! Searching internet first suggested the engine could be from a Güldner, see the picture and description below. But then Philippe came to the rescue and convincingly demonstrates the engine is a Sarolea (photos below); let's assume Sarolea copied the Norton design and not the other way around!
