Thanks for your input Ted, I’m gona try and modify the fmf 125 kart pipe I currently have. The volume is very close to the Bills (after market pipe) that came off the cr250. Unfortunately the fmf expansion chamber length I’m using is 14 ” shorter. I’m trying to do this build on a budget so i’m just going to go for it! This could go horribly wrong but worth a shot.. Wlhen i get everything together I’ll post my findings.