Here we go with porting a Kaw head. This is a must to get the most
out of your engine. This can also be said about most other 2-valve
motors. It is especially applicable to 73-80 Kaw heads. First you
must disassemble the head. Guides must go. You have to replace these
with a good aftermarket set. They go for $45 from APE. You can make
a valve guide arbor out of a steel rod if you have access to a lathe.
You can modify a large c-clamp as a spring compressor. Or you can buy
these things. With the head fully disassembled you can begin.
Clean up the combustion chamber using a wire brush with a Œ" shaft
on a flex shaft moto tool. You will need several wire gauge sizes.
The heavy gauge to clean and fine to polish. Always wear safety glasses.
The wire brushes fly apart. When they start going they make a mess.
I have had these sticking in my arms and chest. I dont know of a better
way to do it.
First blue the sealing surface of the intake ports. You will need a
scribe to mark the port. Clean up your intake manifolds with a half
round file. Do not take more off than you need to. Just clean them up.
Let me be more specific. These things deform after use. If you are
using a stock set they may have deformed inward due to excessive
torque or developed a shoulder. Use the half round file to remove
these deformations. Bolt the manifolds to the head and scribe around
the inner diameter to mark the port.
Here is a close-up of a used OEM manifold bolted on a KZ head.
You will see 2 shoulders. The black shoulder is the manifold.
That shoulder lines up with the inner bore of the carbs you are
using. This particular manifold has a 33mm shoulder after cleanup.
It is actually too small for the 34mm RS carbs I am installing.
I recommend getting new manifolds from any aftermarket source.
Old ones get hard and shrink in size. They make it much more
difficult to install carbs. For the amount of work involved,
this is not a place to save money.
I use a Dremel flex shaft moto tool. The hand piece is visible
in the photo. There are many other brands available. This one
has a Œ" collet in the hand piece. That allows use of large sand
drums and wire brushes.
Here is a close-up. Note how much material must be removed.
This must be blended inward as far as possible. The port must
be at its largest at the surface where you scribed your line.
That way the air-fuel mix will increase in velocity as it flows
through the port. Remove the seams in the ports and take care to
remove all imperfections. You will need a smaller hand piece with
a 1/8" collet to work further in the port.
This is a messy job and care should be taken to minimize the
spread of aluminum dust. The port radius has been increased by
nearly 2.5mm and this cross sectional area has been kept up to
where the guide flow shape starts. The area around the valves has
been cleaned up and polished but no material has been removed.
The exhaust side does not need much work. Use completely compressed
exhaust gaskets to define your hole size. The direction of blending is
opposite for the exhaust. Start as close to the valve as you can and
blend to the end of the port. I use a time limit on each port on the
exhaust side. The exhaust side is much more difficult to port than the
intake. You will use many more sanding drums here.
Here is a finished J model head.
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