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3 Carburetors
Section
Basic
Before attempting any carburetor adjustments
or repairs:
Adjustments
■ Inspect the air filter, and clean if necessary.
All Saws
■ Inspect the spark arrestor for plugging, and
■ Verify that the fuel filter is clean and that the
■ Verify that the chain brake is "off" and that
■ Reset carburetor mixture screws to the
Walbro HDA and
Idle Speed Adjustment (except 357)
WT Carburetor
Figure 3.5
Adjustments
STEP 1. Start the saw and warm the engine to
(except 357, pages
126–127)
STEP 2. Slowly turn the idle speed adjusting
Low Speed Mixture
(engine idling; at operating temperature)
STEP 1. Using a small screwdriver, slowly turn
24
Shindaiwa Inc. 1995
(Section 2)
clean if necessary. (Section 9)
saw's fuel tank is filled with clean, fresh fuel
of the proper octane and mixture (Sections
2 and 14).
the saw chain is free to rotate. (Section 10)
factory-recommended settings shown in the
table (right).
ATTENTION!
■ Mixture screw settings affect both the
performance and durability of any 2-cycle
engine.
■ Overtightening either mixture screw
can permanently damage the carburetor
body!
operating temperature.
WARNING!
The saw chain can rotate whenever the
saw is started!
screw in or out until the engine idles
smoothly at the rpm specified in the table
(above).
the idle mixture screw clockwise (lean
mixture), and note any changes in engine
rpm. Turning the idle mixture screw steadily
clockwise should cause engine speed to
first increase and then decrease as the
mixture becomes leaner.
Basic Carburetor Settings
Model
Idle
Carb
RPM
Model
Adjust
+/-100
High/Low
300
3,000
WYM
12-13
300S
3,000
WYM
12-13
360
3,000
WT89
1
1
357
2,800 WT301B 1
377
3,000
WT229
1
488
2,800
HDA79
1
575
2,800
HDA50
1
577
2,800 HDA50A 1
680
2,800
HDA29
1
695
2,800 HDA29A 1
757
2,500
HDA123 1
1
See also Section 13, pages 126–127
Idle Speed
High Speed
Mixture
57715
Figure 3.5 Carburetor Adjustment Locations
(577 shown)
Carb
Metering
Lever
Height
.059"
.065"/1.65 mm
1
1
⁄
–1
⁄
.065"/1.65 mm
4
4
1
1
⁄
–1
⁄
.065"/1.65 mm
4
4
1
1
⁄
–1
⁄
.065"/1.65 mm
4
4
1
1
⁄
–1
⁄
Level w/body
4
4
1
1
⁄
–1
⁄
Level w/body
4
4
1
1
⁄
–1
⁄
Level w/body
4
4
1
1
⁄
–1
⁄
Level w/body
4
4
1
1
⁄
–1
⁄
Level w/body
4
4
1
1
⁄
–1
⁄
Level w/body
4
4
Low Speed
Mixture
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Troubleshooting
