Yamaha WR250F 2008 Owner's And Service Manual page 109

CHECKING THE AIR INDUCTION
SYSTEM
1. Inspect:
• Air induction hose
Crack/damage → Replace.
• Air induction pipe
Crack/damage → Replace.
2. Check:
• Operation of air cut valve
Pass air through the pipe and
check the air cut valve for opera-
tion.
Does not meet the following con-
dition → Replace the air cut valve
assembly.
"a" to "b" Air passes.
"b" to "a" Air does not pass.
Air does not pass
"a" to "b" when specified pres-
sure is on "c".
• Blow in air to check for operation.
• When using vacuum, check by the
use of the vacuum/pressure pump
gauge set "1".
Vacuum/pressure pump
gauge set:
YB-35956-A/90890-
06756
Vacuum specifying pres-
sure:
46.7–86.7 kPa (350–650
mmHg, 13.8–25.6 inHg)
When using vacuum on the pipe
"c", take care not to exceed the
specified value.
a. From air filter
b. To cylinder head (exhaust
port)
c. From cylinder head (intake
port)
A. Check for induction from air
filter.
B. Check for prevention of back-
flow into air filter.
C. Check for prevention of after-
burn. (When throttle is closed
at sudden deceleration)
5-13
AIR INDICTOIN SYSTEM