Page 28
I
I
I
when it is as lean as safely possible. When you have the bike running well, try leaning out
the needle position and main jet a little at a time, keeping close tabs on the condition of
the spark plug at WOT. (See section III-20) As long as the spark plug test shows a tan col-
ored insulator, you should not be too lean if everything is working properly. A dark col-
ored, oily plug indicates a too rich mixture, while a white, glazed, or light tan appearance
indicates a too lean condition (assuming the spark plug is the proper heat range).
Adjusting carburetor -
Carburetor adjustments can be made without removing the carbu-
retor from the motorcycle.
Idle speed
- The idle speed and fuel metering screw can be
reached with a long screwdriver from the right side of the bike
(left side on X3 & X5). Adjust idle until bike runs smoothly
without stalling when warm. See photo III-47.
Fuel metering screw
-
Adjust fuel metering
screw to fine tune ini-
tial throttle opening
response.
Screw fuel
metering screw in to
lean mixture, screw
out to richen
. The fuel
metering screw is nor-
mally set from 1
1
⁄
2
to
2
1
⁄
2
turns out from fully
seated. If less than 1
1
⁄
2
turns is required to run
properly, install a leaner
pilot jet, conversely, if more than 2
1
⁄
2
turns out is required, install a richer pilot jet. Never tighten fuel metering screw, just gently turn
in until it stops, then back out counting the turns to the desired setting. See photo III-47.
The fuel metering screw can cause overall jetting to be too rich if it is turned out too far. Note that the fuel metering screw only
affects the initial throttle response in conjunction with the pilot jet until the needle jet takes over at
1
⁄
4
throttle and above.
To access the carburetor needle and jets, remove the seat and fuel tank. Loosen the two clamps to the front and rear of the carbu-
retor. Twist the top of the carburetor outward and make note of the proper orientation of the top cover. Remove the two screws and
remove the top cover with the spring, slide and needle attached.
Slide & needle
- To change slide or adjust needle, retract the spring against the top cover. Shake the white plastic retainer out of the top
of the slide or push it out when removing the needle. Adjust the clip position as needed by removing the small clip and snapping it into
another groove. The top groove will cause the needle to run leanest, the bottom groove will cause the needle to run richest. Changing
the needle position causes the needle to reach the tapered portion sooner or later, which causes the needle to richen the fuel mixture
sooner or later. If further adjustment in needle jetting is needed, the needle will have to be changed to a richer or leaner needle. See
specification chart to choose the proper needle. A thicker needle
will provide leaner initial jetting, a thinner needle will provide rich-
er initial jetting. The longer the taper from the pointed end of the
needle, the sooner the needle will begin to richen the carburetor as
the throttle is opened. The diameter of the straight portion of the
needle will affect the jetting from idle to just under
1
⁄
2
throttle, along
with the pilot jet and fuel metering screw. A thicker needle will run
leaner than a thinner one. A needle with a longer taper and a thinner
tip will be richer than a needle with a shorter taper and a thicker tip.
The needle fills the needle jet, so a thicker needle allows less fuel to
flow resulting in a leaner mixture. Optional slides are also avail-
able. The stock 40 slide is available in a metal version, and optional
slides numbered 30 - 60 are available. See photos III-43 - III-45.
To remove the cable from the slide, push the end of the cable into
the slide to free the end of cable from the slide, then withdraw the
end of cable through the larger hole. Reassemble in reverse order,
making sure the needle retainer is fully seated and held by the
spring. When inserting slide into carburetor body, make sure slot in
code
A
mm
B
mm
C
mm
W1
2.46
0.60
24
W2
2.46
0.60
22
W3
2.48
1.40
20
W4
2.48
1.40
18
W5
2.46
1.40
18
W6
2.50
1.00
24
W7
2.50
1.40
18
W8
2.50
1.40
16
W9
2.50
1.40
20
W10
2.50
1.80
16
W11
2.50
1.80
18
W12
2.50
1.80
20
W13
2.50
0.60
22
W14
2.50
0.60
24
W15
2.50
0.60
26
W16
2.50
1.00
22
W17
2.50
1.00
26
W18
2.50
0.60
24
W19
2.50
1.80
20
W20
2.50
1.60
24
W21
2.50
1.60
24
W22
2.50
0.60
26
W23
2.50
0.60
26
W24
2.50
1.80
24
W25
2.50
1.80
22
W26
2.50
0.98
24
Clip positions & effect
Needle dimensions
Needle dimension chart
III
III
.43
.43
III
III
.44
.44
III
III
.45
.45
clip
needle
float
height
Measure float height as shown (remove gasket)
III
III
.34
.34
III
III
.46
.46
