Yamaha MA190, Service Manual

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4-1-3 Unstable speed
TROUBLE CAUSE REMEDY
Knocking
sound
Piston, cylinder or piston ring is worn exces-
sively.
Replace the worn.
Piston pin and piston pin hole are worn
excessively.
Replace piston or piston pin.
Tie rod small head is worn excessively. Replace tie rod.
Roller bearing for crankshaft main shaft is
worn.
Replace roller bearing.
Abnormal
combustion
Engine is too hot Shoot trouble.
Too much carbon deposit in combustion
chamber
Clear away.
Improper gasoline brand or low gasoline
quality
Replace with qualified gasoline.
Spark lacking
There is water in float chamber. Clean.
Improper spark plug electrodes clearance Adjust.
Something wrong with induced coil, and so
on Check and replace damaged
parts.
4-1-4 Unable to ignite
TROUBLE CAUSE REMEDY
Unable igniting
Fuel supply
system
Fuel tank is empty. Refill fuel.
Carburetor is clogged. Check fuel line and dredge.
Float is leaking. Repair.
Needle valve is stuck.
Dismantle float chamber and
eliminate it.
Ignition
system
Spark plug is punctured, or
short-circuited by carbon
deposit.
Replace spark plug.
Side electrode of spark plug is
dropped out.
Replace spark plug.
High-tension wire is dropped
out.
Weld on.
Ignition coil is punctured or
short-circuited.
Replace ignition coil.
Parking wire is located on
engine body.
Find out meeting and insulate.
The other
Cylinder is seriously scored
and valve dropped out. Repair or replace damaged
parts.
4-1 Troubleshooting