Cylinder
Boring & Honing are the most critical machining
procedures performed in any engine. Most shops
under estimate the demand for a quality Boring & Honing
procedure done on a set of cylinders. Over the
years we have found that there are very few shops that
has the capabilities to perform this job correctly.
Most mechanics have been taught to bore a cylinder
to within .002"-.003" of finish size then hone with a
hand held hone using very little pressure and honing oil
and then run a ball hone through the cylinder for a
final touch up. These procedures may have been
acceptable many years ago when engines used cast iron
cylinders with chrome and cast rings, but are unacceptable in today's standards.
With the types of rings manufactured
today it is very important to finish the cylinder so it
has less than .00015"-.00020" roundness and
straightness. The type of finish is also very
critical. If proper crosshatch and finish texture
are not obtained, then it may be impossible for the
rings to seal properly. If the cylinder and rings
cannot achieve proper ring seal the engine will then
have excessive cylinder pressure and oil misting from
the vents.
Hot-Shot Motorworks works very closely
with the piston ring manufactures to insure that we are
up on the latest technologies of piston ring materials
and Boring & Honing procedures. Sometimes we find
that what the ring manufactures recommend will not
necessarily work in air cooled engines as most ring
manufactures work with temperature controlled (water
cooled) engines.
With a temperature controlled engine the engine
temperature rarely sees a cylinder temperature of more
than 190-200 deg. In doing extensive dyno testing
we have found that on certain areas of a cylinder may
reach temperatures of up to 440 deg. With
cylinders reaching these temperatures, it is very
important to hone cylinders with proper equipment so the
cylinder will not become distorted during these
conditions.
Most shops cannot afford this type of
Boring & Honing equipment as it can cost upwards of $35.000.00. It
may be in your best interest to make sure that your shop
sends your cylinder to a specialty shop to have these
procedures performed, and this does not mean send them
to a automotive machine shop to be bored and honed as
they do not have the experience or the proper Torque
Plates and Procedures to perform this on air cooled
Harley-Davidson engines.
It may cost a little more up front, to have your
cylinders sent to a specialty shop, but it will be worth
it in the long run. It may cost another
$40.00-$50.00 more but it sure is a lot less expensive
than having to rebuild your top end again because your
rings didn't seal properly.
Hot-Shot Motorworks specializes in
this type of machine work and can perform this for you
or the shop that you have doing your work.
