Engine Rebuilds – Cylinder Reconditioning vs. Cylinder Resizing

The Tecumseh VH60 is a two-cycle, vertical shaft engine that’s used in tractors and riding lawnmowers. At WeekendFreedomMachines.com, an unofficial website for John Deere enthusiasts, hobbyists swap stories with farmers and gardeners about the best way to keep lawn machines running. In the website’s Restoration Forum, a new member named Walter asked for some advice about rebuilding an old engine.

Walter’s used VH60 was clogged with mud, but his engine problems were bigger than a parts washer alone could solve. Eventually, however, the tractor mechanic freed the cam, released the valves, and salvaged the breather, control plate, and intake. The carburetor was too clogged to save, but replacing it proved easy enough. Next, Walter announced his plans to correct an out-of-round engine cylinder. 

Engine Hones and Out-of-Round Cylinders

The ensuing discussing about engine hones was especially informative. As a mechanic named Kenny explained, ball hones or flexible hones are designed for applications such as cylinder deglazing – not cylinder resizing. For superior surface finishing, the Flex-Hone® tool from Brush Research Manufacturing (BRM) is the right choice. For heavy-duty material removal, a rigid hone is recommended.

In a technical article called Evaluating the Cylinder, the website Small Engine Information agrees. With their continuously-aligned stones, rigid hones are used for removing material from out-of-round or out-of-taper cylinders. After the cylinder is resized, however, surface finishing is required. For optimum lubrication and piston ring seating and sealing, cylinder walls need a series of shallow “scratch marks”.

Flexible Hones and Plateau Finishing

For best results, these scratch marks form a cross-hatch pattern with a uniform series of peaks and valleys. Rigid hones can create uneven valleys, however, so engine mechanics like the ones at WeekendFreedomMachines.com recommend flexible honing tools instead. Self-centering and self-aligning to the bore, BRM cylinder hones mount in a handheld electric drill and are easy-to-use.          

Available for any type or size of cylinder, the Flex-Hone® tool uses a low-temperature abrading process that’s ideal for applications such as surface finishing, deburring, and plateau finishing. BRM engine hones come in small sizes, too, and can be used on many two-stroke engines that would not accommodate a rigid hone.

Have you tried the Flex-Hone® for engine rebuilds? If so, tell us your story by commenting on this blog entry.  We hope to hear from you!