This is an OEM throttle tube from a 2008 Yamaha YZF-R6 with the OEM grip installed. This throttle tube will fit the Yamaha R3.
The OEM throttle tube on the Yamaha R3 requires a very long twist to reach full throttle. The OEM throttle tube on the Yamaha R3 also has molded plastic texture on it to prevent the grip from moving while riding. However, these molded plastic bumps on the throttle make it very difficult to replace the grip with an aftermarket grip. You have to grind off the bumps or they will stick through the new grips.
By replacing the OEM Yamaha R3 throttle tube with this Yamaha R6 throttle tube, you eliminate both of these problems. This R6 throttle tube will shorten the throttle throw by 15-20%. This is very helpful to reduce wrist pressure, and make it easier to twist to full throttle without having to re-grip the throttle. This R6 throttle tube is also smooth on the outside, so you can install any aftermarket grips you like. The only modification to install this throttle tube is to loosen the throttle cable at the adjuster and this is very easy to do in just a few minutes.
For installation on the Kawasaki Ninja 400, follow the instruction in our write up here: How to install an R6 throttle tube in the Kawasaki Ninja 400 / Z400