It is common to replace the throttle tube or throttle assembly on the Kawasaki Ninja 400 to shorten the throttle throw, making it faster and easier to reach full throttle. This is all good, but the shorter you make the throttle throw, the harder it is to twist the throttle, since the force necessary to twist the throttle increases 1:1 as the distance decreases. So if you cut the throttle throw in half with a race throttle system, the force to pull the throttle is doubled and it starts to be annoyingly difficult to twist the throttle and your grips will start to spin.
The Norton Racing Soft Pull Throttle Return Spring is softer than the OEM spring and provides a much lighter, easier pull on the throttle when a race throttle system is installed. This translates to gripping the bars and throttle lighter, better throttle feel and control, and your grips won’t get twisted from twisting the throttle.
Install Video on YouTube: