Originally Posted by RideAbout
Clutch Mod Short.... why does it work?
No one has the full answer. For some reason, Yamaha screws with the engine tuning depending on clutch position. As you probably know, Yamaha uses an electronic throttle on the S10 which means twistgrip position is translated electronically to throttle plate movement by a computer which takes into account many things and apparently the position of the clutch is included. Other bikes do this also so this is not unusual in modern EFI systems.
My personal theory is that Yamaha removes some of the throttle damping and delay inherent in the electronic system to make shifting crisper and let the engine rev more quickly and freely with the clutch pulled. And that's probably all the mod does - you can think of it as a jumpier "super sport" throttle mode that is addition to the sport and tour modes. Others think ignition and fuel mixture may be involved.
Getting the bike past emissions might have also have been a consideration.