Harley-Davidson Cylinder Boring & Honing

All Harley cylinders can be machined to accept oversize pistons in order to give them a new lease of life when they eventually wear out. Some cylinders, such as 883 Sportster and the stock bore Twin Cam can also be machined substantially larger to give a useful capacity increase and resultant performance gain.

bigger bore cylinders, finish machined here to suit our Head Quarters pistons

Harley Twin Cam "bigger bore" cylinders, finish machined here to suit our Head Quarters 113" pistons. With our in-house machine shop and Superflow dyno, we can install, and tune with, any of the parts that we supply.

Boring an iron lined, billet aluminium, big bore Shovelhead cylinder

Boring an iron lined, billet aluminium, big bore Shovelhead cylinder for a custom build

Cylinder boring & honing at Powerglides

Honing 883-1200 conversion cylinders on our Delapena autostroking vertical honing machine.

The popular 883-1200 Sportster conversions are done this way, as are Twin Cam 88-95 and Twin cam 96-103 upgrades. In fact, it is now proven that the Twin Cam 88 can be bored out to 98" and the Twin Cam 96 to 107", all using the stock cylinders as start point. We have pistons available for all applications.

These upgrades are more economical than fitting new cylinders and also offer three distinct engineering advantages. Firstly, even a lightly used cylinder will have undergone a number of heat cycles, which makes it more stable and much less likely to distort in use. Secondly, our Harley specific boring and honing techniques, coupled with our own designed and manufactured torque plates and Auto Stroking Powerhone machine, holds bore size and geometry to plus or minus one tenth of a thousandth of an inch (.0001"). Thirdly, we impart the correct cross hatch pattern and plateaued surface finish onto the cylinder wall which gives very fast piston ring seal, minimum oil consumption and a long service life.

Machining of the Harley cylinders at Powerglides

Many of our Harley Twin Cam performance upgrades involve machining of the Harley cylinders. These 4.060" big bore cylinders are being honed to suit Head Quarters pistons as part of our 113" and 120" conversions.

It is also an unfortunate fact that many new cylinders, out of the box, are badly sized, particularly with regard to out of roundness and taper. By prior arrangement and subject to work load, we can normally offer a same day turnaround on this service. Please note that we do not bore and hone cylinders to suit pistons purchased elsewhere.

Honing of the Harley cylinders at Powerglides

Honing is a very accurate process, with both regard to surface finish and dimensions. Even on a cylinder of this size we can comfortably hold a tolerance of +/- .0001''. Notice also the use of our own designed and manufactureed torque plates which are essential when machining any aluminium Harley cylinder, so as to allow for the distortion that takes place when the cylinders are installed on the engine.

correct cross hatch pattern and surface finish is essential

As well as dimensional accuracy, the correct cross hatch pattern and surface finish is essential for rapid piston ring seal and minimum oil consumption.

For an in depth description of each of the stages in the boring & honing process including an overview of our highly accurate method of measurement, read our boring & honing technical article.

Top

Share |

Powerglides - In The Press