Motorcycle Repair: Very high idle At start, vacuum hose, leak air

Question
1982 Kz1100 D1 Spectre, when first starting the bike will go to @7000 rpm & rising(which I immediately shut it down).I tried to adjust the idle using the idle control knob but either I am totally flooding it or restricting any fuel flow and when trying again no start. which way do you turn the knob to increase fuel flow and any other suggestions?

Answer
Hello Greg,

These multiple carbs can be a bit tricky to
set up. Under normal settings the idle would
not speed up that high.

The idle speed adjuster is a knob down underneath the
carbs. If you are turning any other screws
it could put your carbs out of synchronization.
It requires carburetor vacuum sticks to
get the carbs back in tune with each other then.

A fast idle can be numerous things.
Here are some things to check for:

-Idle screw turned in too far (clockwise)
Turn it left or anti-clockwise to slow down
all the carbs.

-Any loose or leaking carb mounting rubber
could leak air and could cause a high idle
due to lean fuel mixtures.

-A leaking fuel petcock valve diaphragm.
This is in the back of the fuel valve
on the gas tank. If it leaks it can cause
fuel to be pulled into the vacuum hose
and then straight into the engine.
This would likely happen when the engine
is hot or cold.

-Sticky carb slides or sticking
cables or throttle plates in carbs.

-Holes in carb slide diaphragms in top of carbs (if rubber.)

-Misadjustment of carb syncronizing screws.
These are between the carbs and are for
getting all carbs opening and closing at
the same time.

My suggestion would be to look for anything
sticking on the carbs or cables.
Next, turn the idle way down until you
find the cause of the high idle.
Check that the choke is operating smoothly.
It may have a fast idle cam that is interfering
with the throttle plates or butterflies.

You may want to remove the whole carb set and
check that all the throttle plates
close equally and that no carb slides
are sticking.

Set the syncro screws so that all carbs
close fully and open at the same time.

Lastly, check for air leaks around the carb
mounting rubber and check the petcock
valve vacuum line for fuel. It should be
relatively dry.

I believe either something is sticking
on the carbs or you have a vacuum/air leak on
the intake somewhere.

A can of carb spray can sometimes help
to find an air leak on the intake, the engine
will change speed if it draws in the spray.

High engine speeds are usually caused by
a lean fuel mixture unless something is sticky.
This means too much air or not enough fuel
which could be from plugged idle jets in
the carbs.

A good carb soak in cleaning solution and
then a close inspection of carb jets
and components should turn up the problem.

Luck!

Wayne S.
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