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SYNCHRONIZING
MACH III CARBS
KAWASAKI
It is a known fact that if you have
more than one carburetor, one of the
important parts of tuning the engine is
synchronizing the opening of the
throttles. I f you have a twin and one
carb is opening ahead of the other, it
means that one cylinder is doing most
of the work while the other is just
coasting along for the ride. This not
only means that you are not getting full
power; but that you are ovenvorking
the cylinder that is doing all the work.
Also, it can be off just a little and
you may not notice the power loss, but
the engine may wind up with one stuck
piston due to the ovenvork. This is most
ap t to happen on a three cylinder
machine where the lack of one cylinder
doing its job would not be notice as you
would have the other two pulling along.
The
most popular method of
checking for carb sync is to remove the
air cleaners and either look in and watch
'the slides as you open the throttle, or
place your fingers in the orifice and
touch the slides and do it by feel. I am
of the school of thought that this is nOl
the best way. By this J mean that what
you are actually checking is to see that
they are lifting off the throttle stop at
the same time. This does not mean that
they are lifting at the same time. To
better make my point and explain it
further, suppose for some reason or
other you have to adjust the idle screw
on one carb a little higher than the
other. Say you have a bad valve or the
idle jet is plugged or whatever, you still
have the slides at twO different setti)1gi.
At idle, this doesn't hurt anything and
sometimes this is necessary to obtain an
even tickover. [f you adjust your
throttle cables so that they both lift off
the stops at the same time, you are
going to have
.
By R.od Bra.ker
the 500cc H-I. As you mayor may not
know, the F-5 and F-9 Kawasaki
Bighorn 350 is a magneto Capacitor
Discharge Ignition system. Tills gives the
rider a [an tastic spark to insure fire at
1.he plug at all times. In fact the
recommended plug gap is about .045 in.
Thi system will take a COl plug which
is more commonly referred to as a
surface-gap plug. This is the 'coldest
possible spark plug that you can run
into, but the spark put out by the COl
unit will fire it under the most
demanding conditions.
. But where the riders made their
mistake was in the type of COl spark
plug that they used. [n the 500cc unit
which has a battery operated CDr, the
plugs used for this model have a sligh t
space in the core of the electrode, this is
called a booster-gap. What it does in lay
man's terms is provide an open gap
within the plug itself that actually dams
up the spark until it builds up enough
force to jump this' gap. When it does, it
provides a much hotter spark at the plug
than it would have originally. You
applied the same principle when you
pulled the plug wire from a spark plug
that was fouled and held it a short
distance from the plug to clean it out.
What it did was provided a booster gap.
so when it jumped the gap it would
provide a hot enough spark to burn the
fouled deposits. This was a popular trick
to keep tl,e Harley's running in the old
days when they would foul the rear
cylinder.
On the battery ignition COl where
you have a constant voltage [actor, this
booster gap is an asset, bu t on a
magneto COl, it is a liability. This
booster gap causes the coil to ovenvork
and eventually you will wind up with an
electrical problem that will manifest
itself to act like carburetion.
The way you can tell the difference
in these plugs is that on the ones for the
battery operated systems the center
electrode has a small hole through the
center of it. By looking at the top of the
plug, you should be able to see the hole.
This hole is to ventilate the booster gap
to avoid the spark jump from building
up pressure in the gap and thus
increasing the resistance (this happened
on the first CDr plugs). The surface gap
plugs that are safe to use in a Magneto
COl unit do not have this hole in the
top.
.
Champion has recen tly buil 1 a plug
called a UL-17 -v which is a booster gap
plug but it has a wider gap between the
center electrode and the plug body
where the spark jumps to. This in effect
gives you a greater plug gap setting
which is much needed in the 350cc
model. But, as I said, this plug has the
booster gap and should not be used in
the Bighorn as it comes from the box.. If
you wish to adapt one of these plugs,
you can do as I have. I took a paper
clip, straightened it out, and pushed it
down the center of the breather hole.
When 'it had bottomed out, I carefully
soldered it to the very top of the plug
and then trimmed down any excess.
What I did by this was fill in the booster
gap with the paper clip and allowed the
spark to go directJy to the firing gap. I
have been running this same spark plug
in my Bighorn for two years now and
haven't had a bit of problem with it.
So, if you have been running one of
these booster gap plugs in your machine
and you appear to be having carburetion
problems, you migh t get your coil
checked, there is a good chance tnis
could be your problem.
350 KAWASAKI CARB COVER
While on the subject of 350cc
Bighorn Kawasakis, there is one other
thing to look for when you are having
problems. When you first take off the
cover on the right-hand side thal
exposes the carburetor, inside of the
cover you will find a small rubber
grommet that slips over a pip cast in to
the cover. This piece of rubber is called
a cal'buretor push piece.
As this carb just filS into a rubber
'manifold, it is held into place with t,his
rubber push piece. If tll is is removed or
lost when the cover is removed and is
not replaced, it could allow- the carb to
slip out of the rubber manifold and
cause a leak between the carb and the
engine. At the least, it will allow your
carb to bounce around, and in rough
ground this could give your Ooat levels a
beating as well as possibly tear away the
rubber in take manifold.
If you are having a tuning problem
with your Bighorn, you might check
into this, it could save you a lot of time
and trouble.
