Rather than create a single engine to power a number of different chassis, let’s give each bike its own power plant. 500cc is a nice round displacement, so that’s what we’ll make the single cylinder engine in our entry-level bike. If we double that, we get a 1000cc twin, which is a nice size for a cruiser, and we can arrange the cylinders in either the traditional V, or as a parallel—or even flat design. When we triple it, we arrive at 1500cc, which would make an interesting across-the-frame triple. Quadrupled, that gives us a 2-liter four, which could be arranged as a V-four, a flat, pancake-style motor, or in an across-the-frame UJM style.