Yamaha TZ250M, Owner'S Service Manual

Page: 275 / 287

SETTING
7-11
2. Loosen the stand installation bolt
1
, then
rotate the dial gauge stand and set it close
to the center of the piston. Tighten the stand
installation bolt again.
NOTE:
Do not loosen the dial gauge installation bolt
2
while doing the above.
3. Set the piston at top dead center (TDC),
then measure the piston protrusion.
NOTE:
For measurement, avoid the top center pro-
jected area
a
on the piston head but measure
several positions above the piston pin as close
to the center as possible. The average of these
measurements indicates the piston protrusion.
EC71N001
Selection of transmission gear ratio
The following gear sets are contained in the
packing (or optional) to allow the rider to
change the gear ratios according to the circuit
condition or rider’s preference.
CC CAUTION:
Select the transmission gears so that the
number of grooves in the wheel gear match
that of the pinion gear as shown below.
Trouble may be occurred if the selection is
different than that listed below.
a
Groove
TUN
2nd gear
Gear ratio Part number
Number of
groove
Factory installed 31/21 (1.476) 4DP-17221-11/4DP-17121-11 1
Supplying part 27/19 (1.421) 5F7-17221-21/3YL-17121-21 2
Optional part 28/18 (1.556) 5F7-17221-00/3YL-17121-00 –
1st gear
Gear ratio Part number
Number of
groove
Factory installed 34/18 (1.889) 5KE-17211-20/5KE-17411-20 2
Supplying part 28/14 (2.000) 5KE-17211-10/5KE-17411-10 1