Yamaha YZ250FX 2020 User Manual

CAMSHAFT
5-18
5. Measure:
• Camshaft journal diameter “a”
Out of specification  Replace the camshaft.
Within specification  Replace the cylinder
head and the camshaft caps as a set.
EAM30082
CHECKING THE TIMING CHAIN AND
CAMSHAFT SPROCKET
1. Check:
• Timing chain “1”
Damage/stiffness  Replace the timing
chain and camshaft as a set.
2. Check:
• Camshaft sprocket
More than 1/4 tooth wear “a”  Replace the
camshaft and the timing chain as a set.
EAM30083
CHECKING THE TIMING CHAIN
TENSIONERS
1. Check:
• Timing chain tensioner
Crack/damage  Replace.
a. While pressing the tensioner rod lightly
with your fingers, use a thin screwdriver
“1” to wind the tensioner rod up fully clock-
wise.
b. When releasing the screwdriver by press-
ing lightly with your fingers, make sure that
the tensioner rod will come out smoothly.
c. If not, replace the tensioner assembly.
EAM30084
CHECKING THE DECOMPRESSION SYSTEM
1. Check:
• Decompression system
Camshaft journal diameter
21.959–21.972 mm (0.8645–
0.8650 in)
1
1
1
a. 1/4 tooth
b. Correct
1. Timing chain roller
2. Camshaft sprocket
a
b
1
2

Yamaha YZ250FX 2020 Specifications

General

Engine Type	Liquid-cooled, 4-stroke, DOHC, 4-valve
Displacement	250cc
Bore x Stroke	77.0mm x 53.6mm
Compression Ratio	13.5:1
Fuel System	Fuel Injection
Ignition	TCI
Final Drive	Chain
Front Brakes	Hydraulic disc, 270mm
Rear Brakes	Hydraulic disc, 245mm
Length	85.6 in
Width	32.5 in
Height	50.4 in
Seat Height	37.6 in
Ground Clearance	12.8 in
Front Suspension	KYB® Speed-Sensitive System inverted fork; fully adjustable, 12.2-in travel
Front Tire	80/100-21
Rear Tire	110/100-18