The Flex-Hone® for Douglass Motorcycles

Douglass motorcycles dominated dirt track racing during the 1920s, and thrilled speedway racers through the late 1950s. Built by two brothers, William and Edward Douglass, these British motorbikes featured horizontally-opposed twin cylinder engines and a low center of gravity. From 1925 to 1929, some of the world’s best dirt bikers raced the Douglass EW 350 to glory. Even today, these classic motorcycles enjoy a devoted following at Douglass Motorcycle Forum.

Honda Pistons and Douglass Engine Overhauls
During a mid-winter engine rebuild, a Douglass owner named Clive discovered that his bike’s EW pistons were “at the end of the road”. While searching for a “modern substitute” made of low-expansion metal, he pulled the pistons from a 1976 Honda CB750. When the New Zealand mechanic reported that the pistons from the Honda motorcycle had “transformed” the engine in his Douglas EW 350, a Latvian user named Latdoughnut shared his own plans for a Douglass engine rebuild.  

Honing Cylinder Walls with the Flex-Hone®
As part of rebuilding a 350-cc Douglass EW engine “from scratch”, Latdoughnut told Clive how he planned to use the Flex-Hone® tool from Brush Research Manufacturing (BRM) to “finish off the cylinders”. Comprised of abrasive globules laminated onto the ends of flexible nylon filaments, the Flex-Hone® improves internal surface finish while deburring or deglazing cylinders. The tool’s unique construction also allows BRM’s flexible hone to be self-aligning, self-centering, and self-compensating for wear.

Plateau Finishing and Piston Ring Seating
“This abrasive tool,” Latdoughnut continued, “removes torn metal from the cylinder surface” while creating a substantially flat or plateau surface with a cross-hatch pattern. In addition to promoting optimum lubrication, cross-hatching “makes the cylinder surface friendly to piston rings and they bed-in very soon.” By mating the piston rings to the cylinder wall, the engine break-in process creates a seal between the two surfaces. The result is a Douglass motorcycle engine that achieves maximum power with the least amount of oil consumption.