633GC OPERATOR’S MANUAL
21
MAINTENANCE
CARBURETOR
•
The function of the carburetor is to mix fuel with air. The mixture is
adjustable but because the saw has to comply with modern emission
standards, both the Low speed jet, L, and the High speed jet, H, are
limited in travel. Therefore only minor adjustments can be made to
compensate for local conditions like altitude, climate and fuel.
•
The carburetor has three adjustment screws (Figure 12):
T – Idle Screw
is adjusted so that the engine idles smoothly but the
clutch does not engage.
L – Low Speed Jet
is adjusted so that the engine promptly responds to
sharp acceleration but operates smoothly at low RPM.
H – High Speed Jet
is adjusted so that engine produces maximum
RPM and power during the cut.
Adjustment range*
Factory Setting
L
= Low speed jet 1 ¼ to 1 ¾
1 ½
H
= High speed jet ½ to 1
1
* Limited to 180 degrees for emission compliance
•
The jets are limited by a plastic sleeve on the adjustment screw. The H
jet limiter is white (Figure 13) and the L jet limiter is black.
•
Before adjusting the carburetor, make sure the air filter and spit-back
screen are clean and the engine is warmed up.
•
If saw has been running satisfactorily and there is a gradual decrease in
power and drop in RPM at full throttle, the spit-back screen may have
become dirty or the air filter may have become saturated with water.
Clean per page 16.
Figure 12
Figure 13
T
L
H
Summary of Contents for 633GC
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