5.6
Section 5
Fuel System and Governor
Adjustment
NOTE:
Carburetor adjustments should be made
only after the engine has warmed up.
Emission Compliant Non-Adjustable Carburetors
In compliance with current government emission
standards, carburetors on later production engines
are calibrated to deliver the correct fuel-to-air
mixture to the engine under all operating conditions,
without external adjustments, except for low idle
speed (RPM). See Figure 5-5.
Figure 5-5. Emission Compliant Non-Adjustable.
If running performance and troubleshooting indicates
a problem which cannot be rectified by external
means, or adjustment of the low idle speed (RPM)
setting, carburetor disassembly and cleaning may be
required. The basic disassembly and service
procedures for these carburetors remain the same.
Refer to pages 5.6 thru 5.10 as required.
Adjust Carburetor
Low idle speed (RPM) setting:
1. Place the throttle control into the
"idle"
or
"slow"
position. Set the low idle speed to
1500 RPM
(±75RPM) by turning the low idle speed adjusting
screw
in or out
. Check the speed using a
tachometer.
NOTE:
The actual low idle speed depends on
the application - refer to equipment
manufacture's recommendations. The
recommended low idle speed for basic
engines is 1500 RPM.
Low Idle Fuel Needle with Limiter Cap Adjustment:
Some emission compliant carburetors have a limiter
cap on the low idle fuel adjustment screw. Adjustment
is limited to the range established by the cap. Do not
attempt to remove or adjust beyond the limits. See
Figure 5-6.
Figure 5-6.
Adjustable Carburetors
The carburetor on these engines is designed to deliver
the correct fuel-to-air mixture to the engine under all
operating conditions. Adjustable model carburetors
contain adjustment screws for the high and idle
mixtures. If the engine is hard starting, runs roughly
or stalls at low idle speed, it may be necessary to
adjust, clean or service the carburetor.
Adjust To
Midpoint
Rich
Lean
Low Idle Speed
Adjusting Screw
Low Idle
Fuel
Adjusting
Needle
High Speed
(RPM)
Adjusting
Screw
Figure 5-7. Adjustable Main Jet Carburetor.