Big Bore Cylinder Honing - Got 103? - Hot Bike Tech

Here's the aftermath of the initial boring process, resulting in more than one pound of removed material from the cylinder. Both cylinders were treated identically.

After removing the cylinders from the lathe they were handed off to Bob to finish up the job. Each cylinder (with attached torque plates) was successively placed in a Kwik-Way vertical boring/honing machine (top). A close-up of the carbide cutter that was inserted into the Kwik-Way (arrow).

The cutter was adjusted to the bore dimension (from the bore micrometer) before being lowered into place. This particular boring bar removes approximately 20-thousandths of an inch per pass. A single pass took about five minutes.

As the cylinder was getting closer to the desired diameter, Bob grabbed a finer #200 (think of hones like sandpaper grit) multiple pedal-type honing stone, which consists of four rotating stones.

Before beginning, Bob attached the hone to a handheld drill.

He moved the hone up and down, taking off approximately 2.5-thousandths of an inch while producing a smoother surface. A steady supply of honing oil was streaming throughout the entire process. It lubricates and cools the cylinder, as well as washes away debris.

Constant measurements were taken throughout. When Bob was within .5-thousandth from the desired bore diameter, he used a #300 stone that produced a smoother bore than the #200. This was followed up by a pass with the plateau hone to knock off the high spots of the 'peaks' created by the other, coarser, stones.

After thousands of cylinder bore/hone jobs, Bob has a feel for how many passes he needs for each stone. It's as much an art as a procedure. Before removing the torque plates for good, Bob rechecked the bore diameter against the values we measured and calculated earlier. The cylinders were now ready for the 103 piston install.