39mm FCR-MX for the 96-13 DR650SE
In my opinion there isn't another mod you can do that improves performance on the big DR650 like this one does. The stock BST vacuum slide carb just kills the "Thumper" in this bike.
Improvements: Throttle response, low end torque, low speed driveability, reduced decel popping with aftermarket exhaust systems. Superior Keihin carb technology provides: improved jet access, multiple venting points, roller bearing throttle slide with floating seal, completely sealed accelerator pump and throttle cam mechanisms.