Fork Springs - Honda CRF450R Owner's Manual

Fork Springs

The CRF uses a pneumatic spring in the front fork.
The front fork spring rate can be adjusted by
changing the fork air pressure and oil capacity.
The forks on CRF's are about right for riders
weighing between 170 lb (77 kg) and 200 lb (91
kg) (less riding gear). So if you're a heavier rider,
you have to go up on the oil capacity or air
pressure.
Do not adjust the oil capacity or PSF air pressure
to a level that is outside the minimum or maximum
levels.
PSF Air Pressure
• Adjust the PSF air pressure when the fork is cold
as follows:
1. Place an optional workstand under the engine,
so that the front wheel is off the ground.
2. Remove the valve caps and clean the area
around the PSF air valve (1).
(1)
(1) PSF air valve
3. Adjust the PSF air pressure.
Do not adjust the PSF air pressure to a level that is
outside the minimum or maximum levels.
The correct "cold" PSF air pressures are:
standard: 33 psi (230 kPa, 2.3 kgf/cm 2 )
soft (minimum) 31 psi (220 kPa, 2.2 kgf/cm
standard 33 psi (230 kPa, 2.3 kgf/cm
medium-stiff 35 psi (240 kPa, 2.4 kgf/cm
stiff (maximum) 36 psi (250 kPa, 2.5 kgf/cm
with standard oil capacity:
(N) (lbf)
PSF air pressure (MAX)
36 psi (250 kpa, 2.5 kgf/cm 2 )
700
3000
PSF air pressure (STANDARD)
600
2500
33 psi (230 kpa, 2.3 kgf/cm 2 )
500
PSF air pressure (MIN)
2000
400 31 psi (220 kpa, 2.2 kgf/cm 2 )
1500
300
1000
200
500
100
0 2 4 6 8 10
50 100 150 200 250
Stroke (in/mm)
The higher or lower PSF air pressure affects the
entire range of fork travel.
4. Check that there is no air leakage. If there is
any air leakage, replace the air valve assembly.
5. Make sure the valve stem caps are secure. If
necessary, install new caps.
If you need to adjust the PSF air pressure when the
front forks are warm (after driving), refer to page
30.
Front Suspension Adjustments
Oil capacity
• Adjust the oil capacity refer to Fork Assembly on
page 122.
2 )
Oil capacities are:
standard: 8.3 US oz (245 cm 3 )
2 )
2 )
soft (minimum) 7.1 US oz (210 cm
2 )
standard 8.3 US oz (245 cm
stiff (maximum) 8.5 US oz (250cm
When adjusting oil capacity, bear in mind that the
air in the fork will increase in pressure while
riding; therefore, the higher the oil capacity, the
higher the eventual pressure of any air in the fork.
with standard PSF air pressure:
(N) (lbf)
Oil capacity (MAX)
8.5 US oz (250 cm 3 )
700
3000
Oil capacity (STANDARD)
600
2500
8.3 US oz (245 cm 3 )
12 (in)
500
Oil capacity (MIN)
2000
7.1 US oz (210 cm 3 )
300 (mm) 400
1500
300
1000
200
500
100
0 2 4 6
50 100 150
Stroke (in/mm)
The higher or lower oil capacity affects the final
3.9 in (100 mm) of fork travel.
Adjustments for Competition
3 )
3 )
3 )
8 10 12 (in)
200 250 300 (mm)
113