this exhaust is 2.5 outside dia. straight through except for I put a 1 3/4 inch restrictor plate inside about 2 inches from where it hooks to the head. I did this because of back pressure and I ported the exhaust port in the head to about that same dia. 55 pilot jet with the holes and 170 main jet. Its just about right as far as lean or rich goes. I also made a 2.5 inch double k&n intake system.
savage, video, 002