Need some general info about Suzuki GSX 750

Those really were idle air screws, restricting the amount of air that
could mix with the idle fuel. Turning them clockwise richened the
mixture by restricting idle air.

The idle mixture screw on a CV carb is actually adjusting mixture, so
turning it counterclockwise allows more idle mixture to reach the idle
ports.

I have a "super long one", but I don't use it for that. ;-)

No, seriously, a short stubby slot screwdriver works fine, I never had
to remove the gas tank. And, on carburetors that have the idle mixture
screw underneath the carburetor, I use a slot head tip from one of
those screwdriver tip assortments. The tips fit an 8mm socket, but I
can just use the short tip, turning it with my fingers.

My Kawasaki dual sport has a rubber hose going to the airbox, and it
fits in the hole just like the hose on your Suzuki. I push the
Kawasaki's rubber hose back into the airbox to make room to remove the
carburetor.

The clutch spring push between the center hub and the pressure plate.
They don't make the rattling sound, a weak or broken spring would allow
the clutch to slip.

The clutch basket is secured to the tranmission main shaft by a large
nut, it's about 1.25 inches. There is a soft sheet metal securing
washer under the nut. The washer has to be soft enough to bend across
one of the flats of the big nut.

The washer is so soft it will fret under the oscillating loads of
operation. Then the big nut loosen up, allowing the clutch basket to
move sideways on the main shaft. Pulling in the clutch lever pushes
against the pressure plate, and it moves the whole assembly to the
right and the clutch basket rattle
decreases.

The clutch basket has to rotate independently of the main shaft when
the clutch lever is pushed in, so there is a needle bearing or
well-lubricated bushing for the basket to spin on. If the big nut is
loose, the clutch basket will rock slightly on the bearing or bushing
and make noise.

There are also shock absorbing springs arranged in a circle in the
backing plate of most clutch baskets. They help to dampen the
oscillations of the drive train, diminishing shocks transmitted back
and forth between the rear sprocket and the crankshaft. There are
rubber cushions in the rear sprocket to absord shock back there, but
the transmission gears have wide slots for the shifter dogs, so there
is always so driveline slop in that junction which manifests itself
when you roll the throttle on and off.

Sometimes the shock absorbing springs in the clutch basket will just
give up and flop around in their little niches in the soft steel
backing plate. They will make a rattling sound that isn't affected by
pulling the clutch lever in.

I remember the first time I ever heard a piston slap. One of the
mechanics in our Air Force barracks
had a 500cc Matchless scrambler that he raced in the palmetto jungles
of Florida. Every time he twisted the throttle, the loose piston would
make a loud "chuff" sound. I asked the guy if that sound didn't scare
him. He said that it was just piston slap.

"Well, OK, if you say so, it sounds like it's about to self-destruct to
me..."

Excessively rich idle mixture will cause the engine to "8-stroke". It
will fire every other compression stroke and the engine will sound like
it's gargling. As you open the throttle, the engine will clear out the
excess gasoline and run smoother.

When the idle mixture is excessively rich, the engine gargles. When
it's marginally rich, the idle RPM
hangs up after you blip the throttle and slose it. It takes as much as
30 seconds or a minute to idle down again, and that makes the machine
hard to ride in slow traffic, you're always grabbing the clutch lever
and holding it to get the motorcycle to slow down.

Shade tree mechanics don't understand adjustment of the idle mixture
screw on CV carbs. They think that the engine should speed up when they
turn the screw counterclockwise, allowing more gasoline to the mix.

Shade tree mechanics are surprised when the exhaust note becomes dull
and thudding and the idle RPM actually *slows down*.

So they adjust the master idle knob to increase the idle RPM back to
specification, and when they blip the throttle, the idle RPM hangs up.


Shade tree mechanics can't figure out *why* the idle RPM hangs up. It's
because the throttle butterfly is now uncovering the transistion ports,
allowing fuel which is NOT controlled by the idle mixture screw to
enter the airstream.

Your idle mixture screws should probably be set at no more than 1.5
turns open at the beginning, or maybe even less.

On engines with large idle jets ( #42 and up) the idle screws are
sometimes set as little as 0.25 turns open. One engines with small idle
jets ( #35 and smaller ) idle screws may be set as much as 3.0 turns
open.

The difference is due to the fact that the area of the idle jet orifice
varies exponentially as to the square of the radius of the hole....