Re: Whats a 'Looper' and a few other questions
A 'Looper' is a motor with Loop Charged Induction or Loop Scavenged Induction. The other popular design was crossflow.
Here is an excellent description of the two taken from wikipedia.
Crossflow-scavenged
In a crossflow engine the transfer ports and exhaust ports are on opposite sides of the cylinder and a deflector on the top of the piston directs the fresh intake charge into the upper part of the cylinder pushing the residual exhaust gas down the other side of the deflector and out of the exhaust port. The deflector increases piston's weight and its exposed surface area, and also makes it difficult to achieve an efficient combustion chamber shape. This design has been largely superseded by loop scavenging method (below), although for smaller or slower engines the crossflow-scavenged design can be an acceptable approach.
Loop-scavenged
This method of scavenging uses carefully shaped and positioned transfer ports to direct the flow of fresh mixture toward the combustion chamber as it enters the cylinder. The fuel air mixture strikes the cylinder head then follows the curvature of the combustion chamber then is deflected downward. This not only prevents the fuel/air mixture travelling directly out the exhaust port but creates a swirling turbulence which improves combustion efficiency, power and economy. Usually a piston deflector is not required, so this approach has a distinct advantage over the cross flow scheme (above). Often referred to as "Schnuerle" (or "Schn?rl") loop scavenging after the German inventor of an early form in the mid 1920s, it became widely adopted in that country during the 1930s and spread further afield after World War II. Loop scavenging is the most common type of fuel/air mixture transfer used on modern two stroke engines. Suzuki was one of the first manufacturers outside of Europe to adopt loop scavenged two stroke engines. This operational feature was used in conjunction with the expansion chamber exhaust developed by German motorcycle manufacturer, MZ and Walter Kaaden. Loop scavenging, disc valves and expansion chambers worked in a highly coordinated way that saw a significant increase in the power output of two-stroke engines, particularly from the Japanese manufacturers Suzuki, Yamaha and Kawasaki. Suzuki and Yamaha enjoyed success in grand Prix motorcycle racing in the 1960s due in no small way to the increased power afforded by loop scavenging. An additional benefit of loop scavenging was that the piston could be made nearly flat or slightly dome shaped. This enabled the piston to be appreciably lighter and stronger and consequently tolerated higher engine speeds. The "flat top" piston also has better thermal properties and is less prone to uneven heating, expansion, piston seizures, dimensional changes and compression losses.
