Judging Air/Fuel Mixture; Tuning Procedure; Setting Parts And Optional Parts - Suzuki RM250 Owner's Service Manual

4·5 MACHINE TUNING
Judging Air/Fuel Mixture
For proper carburetor tuning , it is necessary to
know how to judge the ai r/fuel mi xture made
in the carburetor ; whether too rich, too lean or
properly mixed. Given below are the symptoms
observed when the engine is not supplied w ith
the proper air/fuel mixture ratio from the carbu·
retor. Check each item as referen ce for judging
the air/fuel mixture condition.
When air/fuel mixture is too rich
1 ) The engin e noise is dut! and intermittent.
2) The engine co ndition becomes wo rse w hen
the choke is applied.
3) Th e engine condition becomes w orse as
it
is
wa rm ed 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 ga s produ ces hea v y smoke.
W hen air/fuel mixture is too lea n
1 ) Th e engine overheats .
2) The engine co ndition 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 powe r is noti ced.
6) Detonation and pinging are experienced .
Tuning Procedure
Th e following indicates the correct tuning proce-
dure for this motorcyc le. Understand the proce-
dure by first riding the motorcycle where it will
be used and adjust the engine to the best con-
dition after judging the air/fuel mixture .
Ca rburetor sta ndard setting
Main jet :
#
180
Jet needle
Slow jet
Air screw
Cut-away
: R1470NS-3rd
#52
1-1/2 turns is out
#5
Setting Parts and Option al Parts
Main je t
Air/fuel
mixture
SIZE P/ND
Lea n
# 170
09491 -34010
# 172 09491 -3 4011
,. #
175
09491 -35009
,. #
1 78
09491 -35010
#180 09491-36008
• # 185
0949 1-3 7008
,. #
190
09491-3801 1
# 195 09491 -39001
#200 09491-400 13
#205
09491-4100 1
# 210 0949 1-42006
#215 09491 -43001
#220
09491 -44006
#225 09491 -45003
Rich
#230 09491 -46004
Slow jet
Air/fuel
mixture
SIZE
P/ND
Lean
#35 09492-35019
# 40 09492-40022
#45 09492-45032
#50 09492-50023
#52 09492-52011
#55 09492-5 5017
Rich #60 09492-60016