Yamaha YTZ250S 1986 Service Manual page 90

Fork spring
In addition to the standard type, two different
type fork springs are sold. A proper spring
should be selected according to the conditions
of a racing course or the weight of the rider.
NOTE: ______________________ _
Always check the oil levels before changing or
re-installing springs.
Type Spring
Spring rate Part
Mark
(kg / mm)
number
Long 0.55
1RX-
23141-00
1-Winding
Std .
Spring seat
1RX-
Short 2.20
23351-00
SOFT
One K\ = 0.4 1RX- 1-winding
spring Kz = 0.5 23351 -10 spring seat
HARD
One
K\=0.5
1RX- 3-winding
spring Kz =0.6 23351-20 spring seat
Air pressure
Although it is possible to change the air
pressure in the forks, it is better to change the
oil level first to gain the desired air-spring ef-
fect. The change in the air pressure affects the
air-spring effect throughout the entire range of
fork travel.
WEIGHT
1. 0.2 kg / cm 2
3. Coil spring
FORK STROKE
2.
0 kg / cm2 (Air/ coil spring)
4-11
• Increase air pressure-+
causes initial load to increase, and the fork
becomes hard.
• Decrease air pressure-+
causes initial load to decrease, and the
fork becomes soft.
Remember, 0 psi air pressure in forks and
release any pressure build-up after each
moto.
1. Place a suitable stand under the engine
to keep the front of machine raised off the
floor. No weight on front wheel.
2.
Using a manual air pump, fill with air.
3. Using the air check gauge, adjust the air
pressure to specification .
4. The difference between both right and left
tubes should be 9.8 kPa (0.1 kg/ cm 2 , 1.4
psi) or less.
Use only air or nitrogen for filling. Never
use any other gas. An explosion may
result.
STD: 0 kPa (0 kg/cm2, 0 psi)
MAX: 5.88 kPa (0.6 kg/ cm 2 , 8.53 psi)
The air pressure should not exceed 5.88
kPa (0.6 kg/ cm 2 , 8.53 psi). Excess air
pressure will cause damage to the forks.
Use only air for filling.