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Incorrect use of choke
Correct use of choke
Incorrect air mixture adjustment
Set mixture adjustment screw in accordance with owner’s
manual instructions
Clogged fuel ilter
Clean ilter
Clogged low speed fuel jets
Disassemble carburetor and chemically clean
Clogged vent in fuel jets
Unclog vent or replace cap
Clogged vent in fuel cap
Unclog vent or replace cap
Float stuck
Remove loat bowl, check loat operation and correct or
replace
Float damaged or leaking
Replace loat
Incorrect loat level
Set loat height in accordance with shop manual specii
-
cation
Intake air leak
Check carburetor mounting langes for air leaks
Ignition problem
Repair, replace, or adjust as necessary
Low cylinder compression
Repair, replace, or adjust as necessary
Idle adjustment(s)
Adjust idle RPM in accordance with speciication in own
-
er’s manual or shop manual
Idle speed adjustments are unequal (twin and multi-car-
buretor models using individual throttle stop adjustments)
Equalize throttle stop settings
Clogged idle & low speed air bleed
Disassemble carburetor and chemically clean
All causes listed under “Hard Starting”
Idle speed set too high
Adjust speed in accordance with speciication in
owner’s manual or shop manual
Clogged low speed air-bleeds
Disassemble carburetor and chemically clean
Damaged mixture adjustment needle
Replace mixture adjustment needle
Mixture adjustment needle “O” ring is not sealing (models
using “O” ring)
Replace “O” ring
Damaged mixture adjustment needle seat
Replace carburetor
Idle speed set too high
Adjust idle speed in accordance with speciication in own
-
er’s manual or shop manual
Idle speed adjustment are unequal (twin and multi-carbu-
retor models using individual throttle stop adjustments)
Equalize throttle stop setting
Throttle valve sticking
Clean and inspect throttle valve and return spring. Replace
as necessary
Throttle linkage sticking
Clean and inspect throttle linkage and return spring. Lubri-
cate, repair, or replace as necessary.
Throttle cable blinding
Correct routing or replace cable as necessary
Incorrect air-fuel mixture adjustment
Low speed - Low speed jet size change.
Intermediate - Jet needle height adjustment
Vacuum piston sticking
Clean and inspect vacuum piston and return spring.
Replace if necessary.
Incorrect choke
Correct use of choke
Clogged air cleaner
Clean or replace
Incorrect air-fuel mixture adjustment
Low speed - Low speed jet size change
Intermediate - Jet needle height adjustment
High speed - Main jet size change
Throttle valve not synchronized
(models with two or more carburetors)
Adjust throttle valve synchronization
Clogged fuel ilter
Clean ilter
Clogged fuel jets
Disassemble carburetor and chemically clean
Clogged air bleeds
Disassemble carburetor and chemically clean
Fuel jet loose
Tighten fuel jets
Fuel jet “O” rings leaking (models using “O” rings)
Replace “O” rings
Float stuck
Remove loat bowl, check loat operation, and correct or
replace
Float damaged or leaking
Replace loat
Incorrect loat level
Set loat height in accordance with shop manual
speciication
Vacuum piston diaphragm raptured
Replace vacuum piston assembly
Ignition problem
Repair, replace, or adjust as necessary
Low cylinder compression
Repair, replace, or adjust as necessary
Problem
Hard Starting
Possible Causes
Correction
Poor Idle or Stalling
Idle mixture adjustment is effective.
Carburetor does not respond to
movement of the idle mixture screw.
Slow return to idle
Engine surges when at a constant speed
Engine does not develop full power, or
misses on acceleration
Carburetor Troubleshooting Guide
529