Het folks ; The wife is wanting to replace/redo the exhaust on her 400F motor. While I can measure the exhaust where it exits the head I don't know what other bikes exhaust downtubes are the same size. Any other bikes have the same size exhaust tubes? The exhaust that's ther has a bad crushed area on the No# 4 tube where it bends to go back that's about 4"+. Plus she's thinking about running 4 into 2 type exhaust. Anybody got any info on the sizes? Thanks, ..cougar...