I just bought a barely used Z125 with a set of china rearsets and noticed that I would have to almost stand on the brake lever to even feel a little brake. First off,the lever is almost 6 inches shorter so it gives less leverage and also puts more tension on the return spring.I removed the return spring and it would lock up the rear wheel with no effort so the fix was to replace the return spring with a longer one or just modify the original one. Cheap easy fix is to get a 3/8" flat washer and attach it to the top of the spring and slip the washer over the post. Works great now.A flat washer with a 1/2" I.D. also works but locks up the wheel a little too easy.