Cylinder Honing for Motorcycle Engine Rebuilds

The Suzuki GS-550 hit the roads in 1977 as the first four-stroke member of the Japanese manufacturer’s motorcycle family. Two years later, Suzuki modified the bike’s styling for the U.S. marketplace, but kept the same great air-cooled, 549-cc, inline-4, 8-valve engine. Built with dual overhead camshafts (DOHC), this high-performance powerplant was part of the Suzuki GS-550 series until the mid-1980s, when a new 674-cc GS-650 engine added more horsepower.

For a GS-550 owner on Do The Ton, an on-line forum for motorcycle enthusiasts, a good deal on a GS-650 engine became a great opportunity for an engine rebuild. Before bolting the top end of the 650 to the block of the 550, the biker tore down his old four-stroke engine. The pistons for the 550 aren’t the same size as for the 650, so rigid honing for bore resizing was probably required. For the final finish, however, the motorcycle mechanic chose a Flex-Hone® tool from Brush Research Manufacturing (BRM).

Flexible Honing for Optimum Lubrication

Built with a stiff, double-wire metal steam and flexible nylon filaments that are permanently laminated to abrasive globules, the BRM Flex-Hone® is versatile, reliable, and easy-to-use. As this Flex-Hone® video shows, BRM engine hones mount easily in variable-speed handheld electric drills. Parts manufacturers often use Flex-Hone® technology with machine centers, but BRM’s cylinder honing tools are a favorite of do-it-yourself (DIY) hobbyists whose equipment is more limited.    

Known also as ball hones, BRM Flex-Hone® tools impart a uniform surface finish along the length of the entire engine cylinder. Unlike honing stones, which can impart an uneven or unidirectional crosshatch, flexible honing tools round and reduce peaks to a consistent height while creating oil-retaining valleys. Rigid honing tools are right for cylinder resizing, geometry correction, and heavy-duty material removal, but honing stones can’t match the Flex-Hone® tool’s plateau finish for optimum lubrication. 

Flexible Hones for Cylinder Wall Surface Finishing 

As the GS-550 owner from Do The Ton explained, BRM provided all of the surface finishing supplies that he needed. After chucking a 240-grit aluminum oxide (AO) Flex-Hone® into his cordless electric drill, the bike-builder lubricated the cylinder honing tool with Flex-Hone® oil, BRM’s specially-formulated blend of honing and lapping oils. The GS-550 owner initially stroked the cylinder too quickly (the Flex-Hone® is a low RPM tool), but eventually achieved the 45-degree crosshatch angle he desired.

BRM’s Flex-Hone® Resource Guide provides guidelines for both tool selection and use, and also explains how flexible cylinder hones are self-aligning, self-centering, and self-compensating for wear. As a full-line supplier of surface finishing solutions, BRM also offers cylinder wash brushes like the one the GS-550 owner ordered. With sturdy bristles made of 6-12 Nylon, these efficient cleaning brushes remove residues from cylinder walls and are designed for use with a mild detergent and warm or hot water.

Wash, Dry, Clean – and Share Your Story 

After washing the cylinder walls, remember to dry each engine cylinder and then clean them with a lint-free cloth that’s coated with a light oil or mineral spirits. Continue to clean until the cloth remains clean. Then, if you’d like to share your surface finishing success story, take a picture of your project and share it with us on Twitter, Facebook, LinkedIn, Google+, or even Pinterest.

BRM also maintains social media channels on YouTube and Vimeo. So if you shoot a video of your flexible honing project, please tell us about it. As the GS-550 owner from Do The Ton demonstrated, Flex-Hone® users have some amazing stories.