Service Manual

3-9
Table of Contents
Two Barrel Carb./Fuel
Twin Cylinder Engine Service Manual
February 2017 - Digital Edition
TWO BARREL CARBURETOR AND FUEL SYSTEM
Troubleshooting
Problem Possible Fuel system
Causes
Next Step...
Engine starts hard, runs
rough or stalls at idle speed
Low speed, RPM setting too slow
Air leak in pilot jet circuit
-Adjust low idle speed to specication
-Inspect pilot jets for blockage or
damaged o-rings
Engine runs rich (indicated by
black, sooty exhaust smoke,
misring, loss of speed and
power, governor hunting or
excessive throttle opening)
Restricted air cleaner lter -Clean or replace air cleaner lter
Choke partially closed during
operation
-Check choke system for proper
operation: cable adjustment, shaft/
buttery not binding, choke spring
length, and debris
Air leak in pilot jet circuit -Inspect pilot jets for blockage or
damage to o-rings
Fuel level too high in float bowl -Pressure test oat and needle
-Inspect oat for cracks or binding
pivot, fuel in oat
-Inspect needle and seat for
dirt/debris/wear ring on needle tip
Bowl vent or air bleeds plugged -Clean vent, ports, and air bleeds
-Blow out all passages with
compressed air.
Faulty Fuel Pump
-Check fuel pump; see “Fuel Pump
Test,” chapter 3, page 3-3
-Check for fuel in pulse line at fuel
pump
Engine runs lean (indicated
by misring, loss of speed
and power, governor hunting
or excessive throttle opening)
Fuel solenoid partially closed -Inspect fuel solenoid for proper
operation or debris, blocked valve
Fuel level too low in bowl -Inspect oat for binding pivot
-Inspect inlet tting for blockage
-Check adequate fuel ow from tank
Blockage in jets, nozzles, or pilot
circuit
-Disassemble and clean: use
carburetor cleaner or ultrasound, then
compressed air only
Fuel Leaks from Carburetor Float not closing needle,
needle not sealing
-Pressure test oat and needle
-Inspect oat for cracks or binding
pivot, fuel in oat
-Inspect needle and seat for
dirt/debris/wear ring on needle tip
Bowl vents blocked -Clean vent, ports, and air bleeds.
-Blow out all passages with
compressed air.
Carburetor gaskets leaking: bowl,
drain screw, fuel solenoid
-Inspect if damaged or mis-assembled
Fuel line leak -Inspect fuel supply line