Honda CRF450R Fork spring minimum oil capacity:
Standard spring: 10.9 US oz (322 cm)
Softer spring: 10.8 US oz (319 cm)
Stiffer spring: 10.7 US oz (316 cm)
The fork should always be adjusted for the rider's weight and track conditions by using one or more of the following methods. Basically, there are four adjustments you can make to the front suspension:
Fork springs – Optional spring is available in softer and stiffer types than the standard rate. (page 10)
Rebound damping – Turning the rebound damping screw adjusts how quickly the fork extends.
Compression damping – Turning the compression damping screw adjusts how quickly the fork compresses.
Oil volume – The effects of higher or lower fork oil level are only felt during the final 3.9 in (100 mm) of fork travel
The fork springs in CRF's are about right for riders weighing between 150 and 160 Ibs (less riding gear). So if you're a heavier rider, you have to go up on the oil level or get a stiffer spring. Do not use less oil than the minimum specified for each spring or there will be a loss of rebound damping control near full extension. If the fork is too hard on big bumps, turn the damping adjuster counterclockwise 1-turn and lower the oil level in increments of 0.2 oz (5 cc) in both fork legs until the desired performance is obtained. Do not, however, lower the oil level below the minimum oil level
For more info, see Honda CRF450R Owners Manual provided by ManualsLib.