Generic Onyx 50, Service Manual

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Diagnosis on abnormal idle speed of engine
Abnormal idle speed of engine
High idle speed No idle speed Unstable idle speed
Check compression
pressure of cylinder Check whether the carburetor
valve is completely closed with
your hand. Check whether ignition is
timely conducted with an
ignition timing light
Insufficient
compression pressure Normal compression
pressure
1. Check whether there
is air leakage in all
outer joints of engine.
2. Check whether air
supply is timely
conducted.
3. Check whether
clearing between
valves is too small.
4. Check whether valve
and valve seat are well
sealed.
5. Check whether
piston ring is ruptured,
blocked in the groove
or lacks elasticity.
6. Check the abrasion
of piston ring and
cylinder.
Adjust the idle speed of
carburetor.
Check
whether idle
jet is too big.
Check whether the
steel wire rope of
accelerator control
cable is flexible
when pulling and
whether the
throttle valve
spring is too soft. Check
whether
the
electrode
clearing
of spark
plug is
too small.
1. Check whether
CDI ignition
device is in
good condition
2. Check whether
flywheels and
trigger coil are
loosened
Idle speed after
adjustment No idle speed after
adjustment
The air adjusting
screws or the
adjusting screws
for throttle valve
are improperly
adjusted. Check whether the
carburetor idle jet, idle
fuel way and air path is
blocked.
Clean and
clear Check whether carburetor float is
placed at high position.
Adjust the float
height to standard
value. 1. Check whether the heat insulator of carburetor
is cracked.
2. Check whether the fixing nuts of carburetor
are loosened.
3. Check whether the vacuum tube of fuel cock
is broken.
4. Check whether air leakage occurs to reed
valve.
Adjust the
electrode
clearing. Check the proportion
of mixed
combustible gas.