MACHINE TUNING 4-7
JUDGING AIR/FUEL MIXTURE
For proper carburetor tuning, it is necessary to
know how to judge the air/fuel mixture made in the
carburetor; whether too rich, too lean or properly
mixed. Given below are the symptoms observed
when the engine is not supplied with the proper
air/fuel mixture ratio from the carburetor. Check
each item as reference for judging the air/fuel mix-
ture condition.
When air/fuel mixture is too rich
1) The engine noise is dull and intermittent.
2) The engine condition becomes worse when the
bypass is applied.
3) The engine condition becomes worse as it is
warmed up.
4) The engine condition improves when the air
cleaner is removed.
5) The spark plug is fouled with carbon (wet and
oily).
6) The exhaust gas produces heavy smoke.
When air/fuel mixture is too lean
1) The engine overheats.
2) The engine condition improves when the
bypass is applied.
3) Acceleration is poor.
4) The spark plug is burned white.
5) The speed of the engine fluctuates and lack of
power is noticed.
6) Detonation and pinging are experienced.
TUNING PROCEDURE
The following indicates the correct tuning procedure
for this motorcycle. Understand the procedure by
first riding the motorcycle where it will be used and
adjust the engine to the best condition after judging
the air/fuel mixture.
Carburetor standard setting
Main jet: #370
Jet needle: 6CHY17-65-3rd
Pilot jet: #42.5
Air screw: 2 turns out
INCLUDED PARTS AND OPTIONAL PARTS
Main jet
Pilot jet
Air/fuel
mixture
SIZE P/NO
Lean #300 09491-60007
#310 09491-62005
#320 09491-64002
#330 09491-66002
#340 09491-68002
#350 09491-70011
* #360 09491-72011
#370 09491-74003
* #380 09491-76003
* #390 09491-78005
#400 09491-80010
#410 09491-82007
#420 09491-84008
#430 09491-86002
#440 09491-88001
#450 09491-90005
#460 09491-92002
#470 09491-94004
#480 09491-96001
#490 09491-98001
Rich #500 09491-10001
Air/fuel
mixture
SIZE P/NO
Lean #25 09492-25011
#27.5 09492-27011
#30 09492-30014
#32.5 09492-32010
#35 09492-35021
#37.5 09492-37003
#40 09492-40028
#42.5 09492-42023
#45 09492-45034
#47.5 09492-47022
Rich #50 09492-50024
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