I found this Honda C70 with 2-cylinder L-twin engine setup on Youtube from Central Java, Indonesia. This mod is extreme considering the 70cc single-cylinder Honda engine is being added with one more additional cylinder. This is like combining two engine into one. Imagine the difficulties in connecting the crankshaft together. The timing of the spark plug. The electronics. The welding of the block. All needs to work perfectly and in harmony.
A great piece of engineering. You can see the video embed after the jump