Honda CRF450RX 2020 User Manual

Valve Clearance
Servicing Your Honda 79
Valve Clearance
Refer to Important Safety Precautions on page 23.
Excessive valve clearance will cause noise and
eventual engine damage. Little or no clearance will
prevent the valve from closing and cause valve
damage and power loss. Check valve clearance
when the engine is cold at the intervals specified in
the Maintenance Schedule (pages 25, 26).
The checking or adjusting of the valve clearance
should be performed while the engine is cold.
The valve clearance will change as engine
temperature rises.
Before inspection, clean the engine thoroughly to
keep dirt from entering the engine.
1. Remove the seat and hang the fuel tank to the
left of the frame (pages 34, 35, 37).
2. Disconnect the breather tube (1) and spark
plug cap (2).
3. Remove the cylinder head cover socket bolts
(3), rubber seals (4), cylinder head cover (5)
and spark plug hole packing (6).
Cylinder Head Cover Removal
(1) breather tube (2) spark plug cap
(2)
(1)
(3) cylinder head cover socket bolts
(4) cylinder head cover rubber seals
(5) cylinder head cover
(6) spark plug hole packing
(5)
(3)
(6)
(3)
(4)

Honda CRF450RX 2020 Specifications

General

Engine Type	449cc liquid-cooled single-cylinder four-stroke
Bore x Stroke	96.0mm x 62.1mm
Compression Ratio	13.5:1
Induction	Programmed Fuel Injection (PGM-FI), 46mm throttle body
Ignition	Full transistorized ignition
Transmission	5-speed
Final Drive	Chain
Front Brake	Single 260mm disc with twin-piston caliper
Rear Brake	Single 240mm disc
Front Tire	80/100-21
Rear Tire	120/80-18
Wheelbase	58.3 inches
Seat Height	37.8 inches
Ground Clearance	12.9 inches
Starter	Electric
Trail	4.6 inches
Front Suspension	49mm inverted fork with rebound and compression damping adjustability; 12.0 inches travel
Rear Suspension	12.4 inches of travel
Valve Train	Unicam, four-valve