2-60
INSP
ADJ
CARBURETOR TUNING
Troubleshooting
Main jet selection chart
Spark plug color
Diagnosis
Remedy
Light tan or gray
Carburetors are tuned prop-
erly.
Dry black or fluffy
deposits
Mixture is too rich.
Replace the main jet with the next smaller size.
White or light gray
Mixture is too lean.
Replace the main jet with the next larger size.
White or gray insulator
with small black or
grayish brown spots
and electrodes having a
bluish-burnt appear-
ance
Mixture is too lean. The piston
is damaged or seized.
Replace the piston and spark plug.
Tune the carburetors again. Begin with low-speed
tuning.
Melted electrodes and
possibly a blistered
insulator
Metallic deposits on
insulator
Mixture is too lean. The spark
plug melted.
Check the piston for holes or seizure.
Check the cooling system, gasoline octane rating
and ignition timing. After replacing the spark plug
with a colder type, tune the carburetors again.
Begin with low-speed tuning.
Trouble
Diagnosis
Adjustment
Hard starting
Insufficient fuel
Add gasoline.
Excessive use of the starter or
choke
Return the starter lever to its seated position so
that the starter valve is fully closed.
Fuel passage is clogged or
frozen
• Check and, if necessary, clean the fuel tank air
vent, the fuel filter and all of the fuel passages.
• Check and, if necessary, clean the carburetor
air vents, fuel passages and the float valve.
• Clean the float chamber of any ice or water.
Overflow
Adjust the fuel level.
Poor idling:
• Poor performance at
low speeds
• Poor acceleration
• Slow response to
throttle
• Engine tends to stall
Improper idling speed adjust-
ment
Adjust the engine idle speed.
Refer to “Low-speed tuning”.
Damaged pilot screw
Replace the pilot screw.
Clogged bypass hole
Clean the bypass hole.
Clogged or loose pilot jet
• Remove the pilot jet, clean it with compressed
air and then install it.
• Make sure that the pilot jet is fully tightened.
Air leaking into the carburetor
joint
Retighten the clamp screws on the carburetor
joints.
Defective starter valve seat
Clean or replace the starter valve seat.
Overflow
Adjust the fuel level.
Summary of Contents for RS90K
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Page 65: ...INSP ADJ ...
Page 158: ...2 57 INSP ADJ CARBURETOR TUNING Guide for carburetion ...
Page 195: ...INSP ADJ ...
Page 659: ... ELEC ...
Page 721: ... ELEC ...
Page 816: ...9 33 SPEC CABLE ROUTING 1 7 2 3 4 6 5 A A A A ...
Page 824: ...9 41 SPEC CABLE ROUTING 3 J K I H G F E D C B A 0 9 8 7 4 5 6 2 1 ...
Page 826: ...9 43 SPEC CABLE ROUTING 3 J K I H G F E D C B A 0 9 8 7 4 5 6 2 1 ...
Page 828: ...9 45 SPEC CABLE ROUTING A B B 1 2 3 4 5 6 7 8 9 0 A B 9 C 0 D E G F B B A ...
Page 830: ...9 47 SPEC CABLE ROUTING 1 5 2 3 4 A B 6 5 7 8 9 0 A C A A B B B A A B ...
Page 832: ...9 49 SPEC CABLE ROUTING A A 7 1 2 3 4 6 5 ...
Page 834: ...9 51 SPEC CABLE ROUTING 1 2 3 4 5 6 7 5 B B A A 8 9 4 4 A A B B ...
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