Yamaha BR250F Service Manual page 39

Trouble Check point Remedy
Adjustment
Poor performance at Clogged air vent Clean
I Remove the air vent pipe, and
normal speeds
clean.
(Relative troubles)
Clogged or loose main jet Clean and retighten Remove main jet, and blow it out
• Excess fuel consumption
• Poor acceleration
with compressed air.
Overflow Check float and float valve
and clean
Poor performance at high Starter valve is left open Fully close valve Return starter lever to its home
speeds position.
(Relative troubles)
Clogged air
vent
Remove and clean
• Power loss
• Poor acceleration
Clogged or loose main jet Clean and retighten Remove main jet, and clean with
compressed air, then install.
Clogged fuel pipe Clean or replace
Dirty fuel tank Clean fuel tank
Air leaking into fuel line Check joint and retighten
Low fuel pump performance Repair pump or replace
Clogged fuel filter Replace
Clogged intake
Check for ice, and remove
Abnormal combustion Lean mix tu res
Clean carburetor and adjust
(Mainly backfire)
Dirty carburetor Clean carburetor
Dirty or clogged fuel pipe
Clean or replace fuel pipe
Overflow
Clogged air vent Clean
(Relative troubles)
Clogged float valve Disassemble and clean Clean
while taking care not to
• Power idling
scratch valve seat.
• Poor performance at low,
mid-range, and high
Scraehed or unevenly worn Clean or replace float valve Valve seat is press-fitted to body.
speeds
float valve or valve seat and valve seat
So body must be replaced if seat is
• Excessive fuel consump-
damaged.
tion
Broken float Replace float
• Hard starting
Incorrect float level
If
not within the specified
• Power loss
• Poor acceleration
range, check the following
parts and replace any
defective part.
• Worn float tang
Replace float Replace float assembly.
• Worn pin
Replace arm pin
• Deformed float arm Replace float