This trick may work on a number of bikes. It’s not new but I find some people are still surprised by the simplicity of the idea. If you’re running aftermarket rearsets chances are that they did not included provisions for the brake switch which also acts as the return spring. A return spring is not absolutely necessary but will provide a positive feel to the brake lever. I know a number of riders don’t find it really important, but you might want to try it.
Placing a spring between the lever arm and master cylinder is simple and very effective.