Yamaha BR250F - Troubleshooting

1. Main jet
G. Troubleshooting
WARNING:
Never remove the main jet cover bolt while
the engine is hot. Fuel will flow out of the
float chamber which could ignite and
cause
damage to the snowmobileand possible injury
to the mechanic.
Place a rag under the carburetor so fuel does
not spread. Place the main jet cover bolt in a
clean
place. Keep it away from fire. After
assembling the carburetor, firmly tighten the
rubber joint
screw. Make sure the throttle
outer tube is in place and the throttle cable
moves smoothly. Clean the carburetor and
allow it to dry.
Trouble Check point
Remedy
Adjustment
Hard starting
Insufficient fuel Add gasoline
Excessive use
of starter
Clean spark
plug
Return starter lever to its seated
(Excessively opened choke)
position.
Fuel passage is clogged or
Clean
Parts
other than carburetor
frozen
• Clogged
fuel tank air vent, clogg-
ed
fuel
filter,
or
clogged fuel
passage
Carburetor
• Clogged or frozen air vent clogged
valve.
• If water collects in float chamber,
clean.
(Also check for ice.l
Overflow
Correct
Poor idling
Improper idling speed
Tighten slow adjuster lightly, and
adjustment
check throttle opening. If incorrect,
(Relative troubles)
•
Slow adjuster
Adjust idling speed
back
it out specification. Start the
• Poor performance at low engine
and
turn slow adjuster in
speeds
and
out 1/4 turn each time. When
• Poor acceleration the engine runs faster, back
out
• Slow response to throttle throttle stop screw so the engine
• Engine tends
to stall
idles at specified speed.
•
Throttle stop screw
Adjust
Tightened to much - Engine speed
is higher.
Backed
out too much
Engine
does
not idle.
Damaged slow adjuster
Replace
slow adjuster
Clogged bypass hole
Clean
Clogged or loose slow
jet
Clean and retighten
Remove slow
jet, and blow
it out
with compressed air.
Air leaking into carburetor
Retighten band screw
joint
Defective starter valve seat
Clean or replace
Overflow
Correct
Poor performance at
Clogged or loose
slow jet
Clean and retighten
Remove slow jet, and blow it out
mid-range speeds
with compressed air.
(Relative troubles)
•
Momentary slow response
to throttle
• Poor acceleration Lean mixtures
Overhaul carburetor
3-7