Initial Setting Throttle Adjust Screw, L Mixture Needle And H Mixture Needle; Adjusting Carburetor - Yamabiko ECHO PB-2520 Service Manual

PB-2520
EB252
6-6-2 Initial setting Throttle adjust screw, L mixture needle and H mixture needle (continued)
A
Fig.1
D
NOTE : The initial carburetor settings for Throttle adjust screw, L and H mixture needles are intended
to start and run the engine before nal carburetor adjustments are made to conform the unit to meet
Emission Regulations. The actual number of turns needed for engine operation may vary.

6-6-3 Adjusting carburetor

E
D
FUEL SYSTEM
A
G
D
A
E
2. Turn H mixture needle (B) clockwise (CW) un-
til lightly seated. And then turn H mixture needle
CCW 1 3/4 turns. Turn L mixture needle (A) clock-
wise until lightly seateds. And then turn L mixture
needle CCW 2 1/2 turns.
3. Turn Throttle adjust screw (D) CW until its head
touches boss (G) as shown in Fig.1. Then turn
G
Throttle adjust screw (D) CCW 13 turns.
1. Start and run engine for 10 seconds at idling
and then run for 180 seconds at WOT.
2. Adjust L mixture needle (A) using 2.5 mm blade
screwdriver (E) to reach maximum engine speed
just before lean drop off .
3. Set idle speed to 3,500 RPM by turning Throttle
adjust screw (D). Engine RPM should be stable at
3,500 RPM after Throttle adjust screw adjustment.
4. Turn L mixture needle (A) CCW to reduce idle
speed 500 RPM to set idle speed at 3,000 RPM.
The idle speed range is 2,800 to 3,200 RPM.
NOTE : Engine speed must be allowed to stabilize
a minimum of 20 seconds after each adjustment
of L mixture needle to assure accurate tachometer
readings.
5. Adjust H mixture needle (B) to obtain maximum
WOT engine speed just before lean drop off using
2.5mm blade screwdriver (E).
6. Turn H mixture needle (B) CCW to reduce WOT
engine speed 10-30 RPM. Minimum WOT engine
speed after adjusting should be over 7,150 RPM.
B
7. Stop and restart engine, and verify engine idle
speed ranges from 2,800 to 3,200 RPM, and WOT
engine speed is over 7,150 RPM. When nal ad-
justment is completed, the engine should idle,
accelerate smoothly, and attain WOT per above
speci cation.
37