2 Stroke Carburetor Adjustment
By: Stu
Thanks Stu! You're the best!
Part 1, The Idle Mixture
It is no surprise that the Idle
Mixture on a brand new Geely Scooter may need to be adjusted when you
receive it. The carburetor is adjusted at the factory where the atmospheric
conditions could be quite different than they are in your area. Fortunately,
it isnít a difficult process for anyone with a small degree of Mechanical
Aptitude. An Inductive Lead Tachometer would be a nice tool to have on hand
for this, but all you really need is a screwdriver and a good set of ears.
Begin by familiarizing yourself with
the scooter carburetor by looking at it. Itís located under the right rear
fender in front of the rear wheel, attached to the engine. On the side of
the carburetor, you will find two brass screws. The screw located farthest
from the engine (on the left as you look at it) is the Air/Fuel Mixture
screw. Turning this screw Clockwise RICHENS the mixture with more fuel/less
air, turning it Counter Clockwise LEANS the mixture with less fuel/more air.
The screw closer to the engine at the base of the ìtowerî is the Idle
Speed Screw. Turning this screw Clockwise INCREASES the Idle Speed, turning
it Counter Clockwise DECREASES the Idle Speed. Memorize their positions, but
donít do anything to them yet. Just identify them so youíll know what to
do later.
The next step is to warm up the
scooter by riding it around for about ten minutes. When the engine is warmed
up, park it on the centerstand in a well ventilated area, and leave the
engine running at idle.
With a screwdriver, give the MIXTURE
SCREW a quarter turn in whichever direction INCREASES the engine idle speed.
IF turning the screw in either
direction causes the Idle Speed to DECREASE, thatís it! Set the screw back
to itís original position, and youíre done already. Move on to the IDLE
SPEED adjustment.
IF turning the
mixture screw in one direction or the other causes the idle speed to
INCREASE, continue turning the screw in that direction another QUARTER TURN
, and listen carefully to the engine speed for a few seconds. Continue doing
this a quarter turn at a time until you hear the engine idle speed begin to
DECREASE, and return the screw setting to where the engine runs at the
fastest idle. As a final touch, give the screw 1/8th turn
clockwise no matter which direction youíve been turning it (to err on the
rich side which runs cooler). Now, youíre ready to set the IDLE SPEED.
Turn the IDLE SPEED screw Counter
Clockwise until the engine sounds like it wants to stall, then Clockwise
again about 1/8th to a quarter turn to smooth it out. The Geely 2
Stroke seems happy to idle at about 1800 to 2000 rpm,
To
summarize the process:
1.
Warm up the engine.
2.
Adjust the MIXTURE screw either way for the fastest idle speed,
(Remember to err on the RICH side by giving the mixture screw 1/8th
turn clockwise from fastest idle).
3.
Adjust the IDLE screw for a normal sounding idle
Itís almost like tuning a radio,
first for the strongest signal, then adjusting the volume to a comfortable
listening level.
A
few things to keep in mind while youíre working on the idle mixture
settings:
…
The Oil Pump is driven by the rear wheel. Every few minutes
when the engine is running at idle, rev the motor up a bit to spin the rear
wheel for a few seconds. That will keep the engine lubricated during the
process, and one reason to do it with the scooter sitting on itís
centerstand.
…
If youíve already been tweaking on the adjustment settings,
and have no idea where the were originally, turn the mixture screw clockwise
until it just stops (- DO NOT OVERTIGHTEN IT! -), then back it out counter
clockwise 1 ‡ turns as a starting point for the procedure. Start the
engine, and set the idle speed screw for a ìnormalî low idle, and begin
the adjustment procedure from step 1.
…
If the warmed up Scooter refuses to idle, or stalls frequently
while idling and this procedure doesnít fix the problem, check for a dirty
air filter, blocked exhaust, or disconnected vacuum lines to the carburetor.
On an older scooter with high mileage, you may need to have the carburetor
and/or exhaust system cleaned, or have the engine tested for leaking seals.
…
Setting the Idle Mixture really doesnít change the mixture
at other throttle settings. From about † to Full Throttle, the mixture is
controlled by jets within the carburetor. Under normal circumstances you
wonít need to bother with them, but if youíre interested, 2 Stroke
Carburetor Adjustment Part II will get into the Mid-Range adjustments.
2 Stroke Carburetor Adjustment
Part II, The Jet Needle
By: Stu Thanks Stu!
* Caution: this is more difficult than Part I. This is offered as reference, we do not support working on your own scooter. You should have a qualified technician work on your scooter. However, we know many of you want to know how things work, so we will continue to provide this valuable information to our customers.
OK,
so youíve adjusted the Idle Mixture on your 2 stroke Geely as described in
Part I, and it runs a lot smoother when you first start taking off down the
road. The only problem is that now youíve noticed that when you get to
about Ê throttle or so, the scooter seems to lag, and maybe even seems to
run slower as you open it up to Wide Open Throttle (WOT). You might suspect
that the Fuel Mixture still has something to do with it, and you might be
right, but donít go back to tweaking on the mixture screw. As stated in
Part I, the mixture screw only affects the fuel mixture from idle to about
† throttle. Beyond that, it has very little effect on the way your Geely
runs in the Midrange.
Fortunately, this is not a
particularly difficult adjustment to make either, and the only tool you will
need is a pair of Needle Nose pliers.
First, crawl back under the right
rear fender, and take another look at the carburetor. You already know about
the Idle adjustment screws, now take a close look at the ìTowerî above
the Idle Speed Screw (the one on the left). You can see where the throttle
cable goes into the top of the tower, and the top looks like it can unscrew
like a bottle cap, doesnít it? Well, thatís because it does!
Donít go playing with it yet.
Start the scooter, and take it for a ride. When the engine is all warmed up,
come to a stop at a place where you can make a long, straight, level run,
and slowly begin to accelerate. Gradually, open the throttle to the point
where the engine feels like itís beginning to lag. Hold the throttle
steady at that position, and gradually push open the choke lever. The
scooter usually will do one of two things. It will either begin to run a
little better, or a little worse. In fact, it might even die altogether if
you hold the choke too far open for too long. If it does, start it up, ride
it around a bit, and try the test again. Do it several times. Be certain
that the scooter responds the same way every time you give the choke lever a
ìnudgeî. Once youíre sure of that, putt back home, shut the engine
off, and get ready to do a little work on your machine.
With the scooter on the centerstand,
reach up under the right rear fender and unscrew the top of the Carburetor
ìTowerî. When itís loosened, lift it straight up to pull out the SLIDE
and the JET NEEDLE. Be gentle, donít yank on it! The cable should be long
enough for you to pull the SLIDE / JET NEEDLE assembly out where you can get
a good look at it. Under the CAP, you should see a spring squeezed into the
cylinder shaped SLIDE, with the JET NEEDLE sticking out the bottom.
First, letís take a good look at
the SLIDE. Notice how the bottom has an ANGLE cut halfway across it. This
ANGLE faces the INTAKE side in the Carburetor. It helps the air mix with the
fuel while the SLIDE acts like a throttle valve. There is also a NOTCH near the bottom and on one side of the
slide. This NOTCH is where the IDLE SPEED screw (not the mixture screw)
fits, and does its job of holding the slide up just a little so the scooter
can idle. On the other side of the SLIDE, there is a GROOVE that runs the
entire length of it. The GROOVE has two purposes. First, it allows the
throttle cable to be removed from the slide, and second, inside the
ìTowerî there is a pin that runs in the GROOVE as the SLIDE runs up and
down inside it. That keeps the SLIDE from twisting and turning as it does
itís job. Itís VERY IMPORTANT to remember all this for when youíre
ready to put it all back together!
Removing the SLIDE from the cable is
easier if you hold the SLIDE ASSEMBLY in your left hand while you twist the
throttle grip with your right hand. The SLIDE will compress the spring. Hold
it together with your fingers as you twist the throttle grip back, and the
end of the cable should poke out the bottom of the SLIDE. Lift the end of
the cable up out of the groove, and let the spring push the slide off the
cable. Hold onto it! You donít want it shooting off to God knows where.
Now, you should be holding the SLIDE
/ JET NEEDLE assembly in your hand. Look inside the slide, and you will see
a hairpin type spring holding the JET NEEDLE in the bottom of the slide.
Reach in there with your NEEDLE NOSE PLIERS to squeeze it gently and pull it
out. Be careful, these things love to jump and hide too. Once the JET NEEDLE
retaining spring has been removed, you can push the JET NEEDLE out of the
SLIDE.
Take a good look at the JET NEEDLE.
You can see it looks pretty much like,Öwell, a needle. Tapered to a point on one end, and the ìheadî has five
little grooves with the worldís tiniest ìEî clip in the middle one.
This is the ìstandardî position for the ìEî clip, and you adjust the
midrange mixture by moving the ìEî clip into a different position.
Hold the JET NEEDLE in front of you
point down, and imagine how it moves up and down inside the carburetor with
the SLIDE. The pointed end fits into a hole in the carburetor called the
NEEDLE JET. Since the NEEDLE JET remains stationary, the taper of the JET
NEEDLE allows more or less fuel to mix with the incoming air depending on
the thickness of the taper that remains in the NEEDLE JET. Moving the JET
NEEDLE up lets MORE fuel into the airstream. Moving it down lets LESS fuel
into the mix. You change the midrange air / fuel ratio by making the JET
NEEDLE move higher or lower in relation to the SLIDE. All you need to know
is which way to move it.
Remember your test ride when you
turned on the choke lever? That temporarily added more fuel to the mix. If
your scooter ran BETTER, then the midrange mix is lean, and you need to move
the ìEî clip one notch down toward the pointed end. If your scooter ran
WORSE, then the midrange mix is rich, and you need to move the ìEî clip
up one notch toward the ìheadî end. Decide now which groove youíre
going to put it in, but donít move it more than one notch at a time or you
might adjust it too much.
The easiest way to remove the
ìEî clip is to lay the JET NEEDLE on a hard, flat surface with the
opening of the ìEî clip down. Cover it with your hand or a cloth in case
the little clip decides to make a leap for freedom, and press the JET NEEDLE
partly out the opening. If the clip doesnít pop off, grab it
tightly with your needle nose pliers and carefully pull it off the rest of
the way, (if you do lose it, you can get another at most Hardware stores).
Using the same hard, flat surface
method, press the ìEî clip back onto the NEEDLE JET in itís new
position, making certain that itís completely snapped into place in itís
new groove. Drop the JET NEEDLE back into the SLIDE, and replace the hairpin
type JET NEEDLE retaining spring with your pliers, pushing it all the way to
the bottom of the SLIDE. Make sure the JET NEEDLE stays in place when
youíre done.
Now comes the hardest part. You have
to put the SLIDE SPRING onto the throttle cable where it sticks out under
the Tower Cap, and squeeze it past the little ball on the end of the cable
as far as you can. Donít get frustrated, I swear it can be done with some practice.
Fit the little ball end into its
special place in the bottom of the slide groove, and pull the cable into the
groove as you push the spring up and over the top of the slide and let it
pop into place.
Gently, put the SLIDE / JET NEEDLE
assembly back into the ìTowerî of the carburetor. DO NOT FORCE IT! It
will practically fall inside when you have it lined up right. Remember to
keep it properly oriented as described before. Jiggle, twist, up / down,
play with it until it slips inside the Tower all the way to the bottom, and
screw the cap back on. If you have to push the cap down to compress the
spring more than a millimeter or two, it isnít right. Pull it out and try
again.
Once you have the Carburetor back together, take another test ride, (You may want to re adjust the IDLE mixture per Part I of this series). Hopefully, your scooter will accelerate much more smoothly than before. If not, then go back to the beginning and try the ìChokeî test again to determine if the ìEî clip needs to be moved yet another groove up or down. When in doubt, leave it in the center JET NEEDLE groove as thatís the standard position set by the factory, and be happy you saved yourself the $40 a bike shop would have charged you to do the same thing!
Fuel Leaks
It's important that you don't operate your scooter if it leaks fuel or
oil. Have a professional work on it if you are not familiar with small
engine repair. These tech tips assume you have some mechanical ability.
Checking for fuel leaks are simple. Just find the wet area and fix the
problem. (1.) Make sure the lines are connected to the carburetor. See
the picture below with the letter "D"; this is the fuel line
connection to the carburetor. (2.) Check all of the lines from the fuel tank
to the carburetor and make sure they are tight. (3.) A common problem is fuel
leaking from the clear over flow line. This is caused by one of two
things. (a.) the choke is stuck, replace the carburetor with a new unit.
(b.) The screw at the bottom of the bowl is not tight. Se the picture below
and tighten the screw marked "A".
The transfer case only needs 100ml of 10W-30 motor oil. In warmer climates,
10W-40 would be fine. The clutch shares the space with the chain oil
system, so if you over fill the oil you will destroy the clutch and void
your warranty. The filler hole is marked "E" in
the picture below. The drain plug is marked "F". The
screw marked "G" is the safety filler screw. Remove this screw
while re-filling the oil and you will be sure not to trash your
clutch. The oil will simply drain out of this hole before getting too
high and touching the clutch.
The picture below shows the clutch and driveline. You can see that the
clutch could get too much oil if you over fill it, so please follow the
manufacturers instructions and only use 100ml of oil. The oil should
never go over the line marked "H" in the picture below.
