The Flex-Hone® for the Kawasaki ZRX1200

The Kawasaki ZRX1200 is a standard motorcycle or “naked bike” with a liquid-cooled, 1164-cc, in-line four cylinder engine. Built to remind riders of the simple-but-powerful Universal Japanese Motorcycle (UJM) of the 1970s, the ZRX features Nikasil-plated, aluminum engine cylinders that weigh less than the cast iron or steel-lined cylinders used in some classic motorcycles. As a cylinder liner, Nikasil reduces wear and friction – even in very large cylinder bores with tight tolerances. Over time, however, even Nikasil-plated engine cylinders need flexible honing to restore their crosshatched pattern.

Crosshatching and Engine Lubrication
As the motorcycle mechanics at DragBikeZone.com know, cylinder walls won’t retain adequate oil without a crosshatched pattern of properly-angled grooves. In addition to causing engine problems such as wear and chattering, improper engine lubrication can prevent piston rings from properly seating during break-in. That’s why an experienced Kawasaki ZRX1200 owner named rgeorge chose the Flex-Hone® tool from Brush Research Manufacturing (BRM) for his engine rebuild project.

After discovering that all four of his bike’s cylinders had “much noticeable wear” but were “still perfectly round”, rgeorge used an flexible engine hone from BRM to restore the cross-hatch pattern needed for proper oil retention and sealing. The Flex-Hone® tool that he chose was an 83-mm, 240-grit aluminum oxide (AO) engine hone. “These flexible hones are oversized to provide preload to the cylinder walls,” the biker explained, noting that his cylinder bores are 84-mm.      

Cylinder Honing for Plateau Finishing
Built with a coated metal stem and flexile nylon filaments, the Flex-Hone® features abrasive globules that restore crosshatching and impart a plateau finish. Self-centering and self-aligning to the bore, the Flex-Hone® is not a material removal tool. Although it will not correct out-of-roundness or remove taper from a cylinder, BRM’s flexible hone is ideal for freshening a cylinder prior to re-ringing.

As a biker named Y2KZX12R added, “a plateau finish is what modern bike cylinders need to have with these low tension hard rings”. For his part, rgeorge was plenty pleased with his cylinder measurements. After using the Flex-Hone® to restore the surface finish, the mechanic measured each engine cylinder in six places: top, middle, and bottom; front to back; and side-to-side at each height. “The cylinders were still perfectly round,” he reported, “front-to-back or side-to-side made no difference”.