Some
engines have transfer ports through the piston as seen here
and the picture below. This is a Schnuerle ported RJL K.61 and
it has a large transfer window in the piston for the boost port.
These ports in the piston are always opposite the exhaust. If
you were to put this piston in backwards all the crankcase compression
would leak out and the engine will not run.
This
is a loop scavenged piston & cylinder out of a K&B 40.
This has the transfer holes n the piston and cylinder. I refer
to these as cheater holes because you can increase the flow
through the bypass without altering the crankcase casting. This
trick has been done for 60+ years.
You
can always tell a loop scavenged engine by the baffle on top
of the piston. On a loop scavenged engine, the baffle ALWAYS
goes opposite the exhaust ports.
The
exhaust port or ports are always symmetrical and are ALWAYS
THE HIGHER PORTS. Closer to the top of the cylinder. Like this
example you can see the "cheater holes" on the left
and the higher exhaust ports on the left.
Sometimes
there is no web or bridge between the exhaust ports, so you
only have one wide, rectangular port.
The
above information is provided as a guide. Since MECOA/K&B has
no way of determining the ability of the individual using and understanding
this information, we assume absolutely NO RESPONSIBILITY for any
damage to person or property from the use of this information.