Race motorcycles are the pinnacle of everything to go fast and nothing else. Of course, Jay Leno happens to have a few of interest in his collection, including the pre-war Scott Flying Squirrel that he takes for a ride on this week’s episode of Jay Leno’s Garage. The styling of the bike matches up with other bikes of the 1920s, but that is where most of the similarities end.
For example, the Flying Squirrel has a radiator tucked up front under the nose of the fuel tank. The majority of bikes in the pre-war era relied on the simplicity of air-cooling over the complex casting and fitment required to liquid-cool an engine. The system is still relatively rudimentary though, with no water pump to force coolant through the passages. Instead, physics does the work and it is called thermo-siphoning. The hot water in the engine case rises to the radiator, forcing the cooler water of the radiator into the engine case to cool the twin cylinders. This is the same system used on 1908–27 Model T Fords, though the new-for-1928 Model A got a water pump.
Furthermore, this engine is a two-stroke, which makes it much simpler to produce as there is no valvetrain that requires precision machining. Instead, the piston assumes the job of the valves, uncovering ports cut into the cylinder wall, which allows the spent combustion gases to exit stage left while a fresh charge of fuel and air are pulled on the other side. Of course, some fresh air and fuel are likely pulled directly through the exhaust port, making two-strokes less efficient that their four-stroke counterparts until the arrival of direct fuel injection.
How well does this combination of rudimentary systems work? Quite well, actually. Jay takes the bike out for a spin on a warm California day with no overheating or goofy problems. It also has the power to safely ride in modern traffic. Sure, the whole hand shift thing will take some getting used to, but it looks like a pretty rewarding experience to motor around on a pre-war race bike like this one.