reed valves generally float around the 10500 RPM mark, and make more torque. Piston port will give more rpm and performance but will sacrifice duration of port open timing. rotary valve will give most duration and RPM but will sacrifice low end torque I guess it depends on what the application...
An idea off the wall here is that gasoline is a oil and depending on your geographical location there are many diffrent blends of gasoline diffrent times of the year hot locations have a more oily fuel and cold locations have a "dryer" fuel. With hot weather fuel being more oily then cold...
