The front brake on my 2020 Kawasaki KX450 doesn’t feel as powerful as I think it should based on past experience with four Kawasakis. I bled the brakes with high-temp brake fluid, measured the thickness of the relatively new brake pads, and roughed up the front rotor with 600-grade sandpaper. But, the brakes still lack pizazz. What do you think the problem is?
One of the problems with modern motocross electronics is the hardware, buttons, switches and perches that end up on the handlebars. In the case of the 2020 KX450, the 7/8-inch crossbar-equipped handlebars add two additional clamps to the already crowded bar space. From left to right, you have the grip, kill button, clutch perch, map switch and crossbar clamp, followed by the right-side crossbar clamp, brake master cylinder perch, electric-start button, throttle housing and grip. With the curvature of the handlebars downward towards the triple clamps, space is at a premium.
We first noticed this crowding with the 2020 Kawasaki KX450 clutch. We wanted to move the clutch lever inboard to make more room for the lever’s arc (in an attempt to pull it in farther). We couldn’t do it, so we consulted ARC lever designer Bob Barnett, who makes Eli Tomac’s clutch levers. He suggested a clutch lever that had adjustable leverage ratios. That solved our clutch problem.
So, when we got your email, we called Bob and asked him what the source of your brake problem was. Bob dropped this gem on us. “Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.” We recognized the quote from Greek mathematician Archimedes (287–212 BC) but told Bob that we didn’t know that Archie had ever raced. Bob said that the cause of your problem was most likely where you were pulling the brake lever from. According to Bob, via Archimedes, the difference between pulling the brake lever in the middle or farther out towards the end is 30 percent more leverage. Bob suggested that you slide your brake perch farther inboard on the handlebars so that you are pulling the brake lever farther away from its fulcrum—noting that with a long enough brake lever, you could “move the world.”
The basis of Bob’s simple advice is that your brake lever pushes against the fluid trapped in the brake line. The fluid moves easily when you first pull the lever but puts up increasing resistance as it compresses the brake fluid in your front caliper. By using Archimedes’ principle, which refers to the displacement of a fluid, you will be able to apply more force on the brake fluid with a longer lever (or by simply moving your finger farther outboard on the lever).