Sealing The Carburetor; High Altitude Tuning - Yamaha BR250F Service Manual

C. Sealing the Carburetor
ALWAYS seal the carburetor before turning
a snowmobile on its side for service. This will
prevent fuel from spilling and creating a
hazard.
1. Plug the fuel-tank vent pipe.
2. Plug both float-bowl overflow pipes or
connect them together.
3. Drain float bowl.
1-7. HIGH ALTITUDE TUNING
To attain the best performance in high altitude conditions, carefully tune the snowmobile as out-
lined below.
Confirm STD settings
• Carburetor (Page 3-3)
• Ignition timing (Page 6-2)
• Spark plug (Page 6-5)
+
Adjust main jet size according to the chart
!
(Page 3-3)
Test main jet size
(performance & plug colour)
Not OK
~
Adjust main jet size
(Page 3-6)
•
I
I I
Not OK
Not OK OK
I
OK
Check to see if gearing is too high or low
NotOK OK
Adjust gearing as required
(Page 4-12)
OK Not OK
Not OK OK
Check engagement speed and
shift performance
Not OK OK-----r~
High altitude
tuning OK
Adjust primary clutch as required
{Page 4-1)
NotOK
OK
Not 01<..
Adjust secondary clutch as required
{Page 4-1)
OK
1-5