Yamaha TZ125M1 Owner's Service Manual page 244

SETTING
When the cylinder gasket is changed, measure
the protruding (or sinking) amount of the piston
above (below) the cylinder top and then
change the cylinder gasket so that the follow-
ing approximate relation can be achieved
between the temperature and the piston pro-
truding amount. (The table shows an example
when the air pressure is 1013 hPa (760
mmHg).)
C C CAUTION:
• Piston protruding amount must be a max-
imum 0.15 mm (0.006 in). Above this value,
the piston and cylinder head may contact
each other.
• As the air pressure becomes lower at a
higher altitude, slide to the right the tem-
perature scale readings by 10°C (50°F)
each for every change in the air pressure
of 27 hPa (20 mmHg).
• Too much random piston protrusion at low
temperature may develop an abnormal
combustion (detonation), which may
adversely affect the intended performance
of the engine.
A Air temperature
B Piston protruding amount
EC71T000
Cylinder gasket setting parts
Part number
4JT-11351-02
4JT-11351-12
4JT-11351-22
* Factory installed
EC71L002
Measuring piston protrusion
1. Install the dial gauge 1 and dial gauge
stand 2 to the cylinder contact surface and
set the scale of the dial gauge to zero.
C
Dial gauge:
YU-03097/90890-01252
Stand:
YU-01256
7-10
TUN
Size (thickness)
* t=0.8 mm (0.031 in)
t=0.7 mm (0.028 in)
t=0.6 mm (0.024 in)