Brake Mod (Master Cylinder)

Budget Brake Improvement

By Harl Hoppler

This procedure is an easy and cost effective way to improve the stopping power of your Sprint ST brakes. The stock master cylinder on an ST is a 14mm Nissin. Many Japanese sportbikes use a 5/8" Nissin master cylinder. Among those are late model Kawi ZX6/7/9R and Honda CBR900RR, probably others as well. The cylinder size is cast into the side of the master cylinder. Why the smaller is a metric measure and the larger English is one of the great mysteries of our time. FWIW 14 mm is about 9/16" and 5/8" is about 16mm. Anyway, each lever stroke with the larger cylinder pushes about 25% more fluid. While the Nissin master cylinder doesn't have the massive 19 mm piston of the Brembo swap, it's dead simple to install, offers significant improvement, and costs less than half as much. And you can use your stock lever (with minor mods), fluid reservoir and mount, and brake switch. Depending on the cylinder you get, you might even get a tapped hole on the body that will allow you to mount the fluid reservoir someplace nicer looking than the fugly handlebar mount Triumph provides on the 2001. Less prone to put a kink in the hose, too.

Pic 1 shows both cylinders from the bottom, the stock unit on the right and a '99 CBR unit on the left. The arrow in the pic points to their only significant external difference, an extension on the CBR unit that must be removed. I used a bit of judicious hacksaw. Make sure you don't get any metal swarf in the master cylinder when you whack the piece off.

Pic 2 is the Sprint brake lever. The arrow points to a recess that has to be filled to use the lever. Actually, you can use the lever without the mod. Your brakes will work; you just won't have any brake lights as the recess prevents contact with the brake switch. I cut a little piece of aluminum sheet about the correct thickness, drilled and tapped the lever, and screwed the bits together with some JB Weld as additional security. Or, the lazy but easy method would be to buy the correct brand/make lever, but the color might not match. And my local parts house didn’t have one anyway.

Pic 3 is the new cylinder, installed. I used a Lockhart banjo bolt with bleeder that makes bleeding the brakes easier. Makes setting preload a bit harder, though, as the extra length of the bleeder partially covers the adjuster slot. The Lockhart PN for a Honda or Kawi is 408-1001.

Takes a couple of hours to swap the bits out, a bit more by the time your screw with modifying the lever. How does it work? Great. After a week long trip to run some excellant twisties, feel is still excellent and stopping power definitely seems better. True two finger breaking and it hasn’t lost feel or suffered from increased travel with time, like the stock unit.

I got the master cylinder at my local Triumph dealer, who also happens to be a salvage yard that specializes in sport bikes, Erico Motorsports,