Honda CRF450R 2009 Service Manual page 59

PSF (PNEUMATIC SPRING FORK) (,13 -
'14)
TECHNICAL FEATURE
This motorcycle has forks which use a pneumatic spring instead of steel , - - -- -- -- - - - -- - - - - - - ,
springs. RETURN PISTON
The spring rate can be adjusted by changing the air pressure and oil AIR VALVE RUBBER (REBOUND)
capacity, instead of swapping the steel springs which requires fork
disassembly.
PSF
consists of
the following components:
Air .... alve: to adjust the PSF air pressure
Return rubber: assists the free piston when returning .
Free piston: separates the air chamber from the oil chamber in the
damper.
Pistons (compresslonfrebound): control the damping of the fork.
Rebound spring : compresses when the fork is fully extended.
Balance spring : balances the resistant force (air spring ) by generating
an extensive force when the fork is in neutral-to-fully extended stale.
The room for the air becomes less under compression stroke. The resistant
force increases as the sealed chamber decreases in volume.
The oil flow in the damper is the same as that of conventional cartridge
forks.
When extended:
FREE PilSTON
When compressed:
FORK DAMPER
The volume
of air
Ch,oml"" decreases.
OUTER TUBE
OUTER TUBE
I) ,
FREE
. ~PISTON
,
I
REBOUND
SPRING
PISTON
(COMPRESSION)
- I
D - OIL
D , AIR
DAMPER
FORK SUDER
Oil now:
When extended :
When compressed :
BALANCE
SPRING
2-5