Adjusting The Carburetor; Adjusting The Engine Idling Speed - Yamaha TT-R90(W) Owner's Manual

Adjusting the carburetor

The carburetor is an important part of
the engine and requires very sophisti-
cated adjustment. Therefore, most car-
buretor adjustments should be left to a
Yamaha dealer, who has the neces-
sary professional knowledge and expe-
rience. The adjustment described in the
following section, however, may be ser-
viced by the owner as part of routine
maintenance.
CAUTION:
The carburetor has been set and ex-
tensively tested at the Yamaha fac-
tory. Changing these
without sufficient technical knowl-
edge may result in poor perfor-
mance of or damage to the engine.
PERIODIC MAINTENANCE AND MINOR REPAIR
EAU39930
Adjusting the engine idling
speed
The engine idling speed must be
checked and, if necessary, adjusted as
follows at the intervals specified in the
periodic maintenance and lubrication
chart.
NOTE:
A diagnostic tachometer is needed to
make this adjustment.
ECA10550
1. Attach the tachometer to the spark
plug lead.
2. Start the engine and warm it up for
several minutes at 1000–2000
settings
r/min while occasionally revving it
to 4000–5000 r/min.
NOTE:
The engine is warm when it quickly re-
sponds to the throttle.
3. Check the engine idling speed
and, if necessary, adjust it to spec-
ification by turning the throttle stop
screw. To increase the engine
idling speed, turn the screw in di-
EAU21360
1. Throttle stop screw
NOTE:
If the specified idling speed cannot be
obtained as described above, have a
Yamaha dealer make the adjustment.
6-13
rection (a). To decrease the en-
gine idling speed, turn the screw in
direction (b).
Engine idling speed:
1400–1600 r/min
6