yah, single cylinder vehicles pretty much need a flywheel to keep running, which makes the aluminum blade lawnmower test a bit of a red herring. The lower the rpm you want to run at the bigger flywheel you need. Multi-cylindered vehicles, are less needing of a flywheel, since there are more power pulses and more roatating mass to carry the cylinder compressing through to ignition.
FYI, here is a nice DMF animation, for NVH fans everywhere