Suzuki RM 250 2003 Owner's Service Manual page 91

9-8 FUEL SYSTEM
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
choke 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 choke
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: #172
Jet needle: NEDH-4th
Slow jet: #50
Air screw: 1 and 1/2 turns out
Cut-away: #7
Power jet: #55
Included Parts and Optional Parts
Main jet
Air/fuel
SIZE
mixture
Lean #150
#152
#155
#158
#160
#162
#165
* #168
#170
#172
* #175
#178
#180
#185
#190
#195
#200
#205
Rich #210
Slow jet
Air/fuel
SIZE
mixture
Lean #35
#40
#42
#45
#48
#50
#52
#55
#58
Rich #60
P/NO.
09491-30018
09491-30019
09491-31012
09491-31013
09491-32010
09491-32011
09491-33009
09491-33010
09491-34010
09491-34011
09491-35009
09491-35010
09491-36008
09491-37008
09491-38011
09491-39001
09491-40013
09491-41001
09491-42006
P/NO.
09492-35019
09492-40022
09492-42019
09492-45032
09492-48013
09492-50023
09492-52011
09492-55017
09492-58001
09492-60016