Troubles Diagnosis; Engine Hard To Start Or Can Not Be Started - Sym JET 4 R 50 Series Service Manual

TROUBLES DIAGNOSIS

A. Engine hard to start or can not be started
Check and adjustment
Loosen carburetor drain bolt
to check if there is gasoline
inside the carburetor
Fuel supplied tom
carburetor sufficient
Remove spark plug, install
it into spark plug cap, and
perform a spark test
against engine ground.
Check if sparks
Perform cylinder
compression pressure test.
Cylinder compression
pressure normal
Re-start by following the
starting procedures
No ignition
Remove the spark plug
again and check it.
Dry spark plug
Remove carburetor after 30 minutes
and connect a hose onto fuel rich
circuit. Then blow the hose with air
Blowing in normal
1. GENERAL INFORMATION/TROUBLE DIAGNOSIS
Fault condition
No fuel is supplied to
carburetor
Weak sparks, no spark
at all
Low compression
pressure or no pressure
There are some signs of
ignition, nut engine can
not be started
Wet spark plug
Blowing clogged
Probable causes
1. No fuel in fuel tank
2. Check if the pipes, fuel tank to
carburetor and intake vacuum,
are clogged.
3. Float valve clogged
4. Lines in fuel tank evaporation
system clogged
5. Malfunction of fuel pump
6. Loosen or damaged fuel pump
vacuum hose
7. Fuel filter clogged
1. Malfunction of spark plug
2. Spark plug foul
3. Malfunction of CDI set
4. Malfunction of AC generator
5. Ignition coil is in open or short
circuit
6. Ignition coil leads open or short
circuit
7. Malfunction of main switch
1. Piston ring seized
2. Malfunction of cylinder valves
3. Worn cylinder and piston ring
4. Cylinder gasket leak
5. Sand hole in compression parts
Crankcase leakage for
6.
pre-compression
1. Malfunction of throttle valve
operation
2. Air sucked into intake manifold
3. Incorrect ignition timing
1. Fuel level in carburetor too high
2. Malfunction of throttle valve
operation
3. Throttle valve opening too wide
1. Malfunction of automatic by-
starter
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