Yamaha YZ250F 2016 Service Manual

CYLINDER AND PISTON
5-33
EAS1SM9228
CHECKING THE PISTON PIN
1. Check:
• Piston pin
Brown or silver discoloration/excessive
wear/pitting/scratches/grooves  Replace
the piston pin and then check the lubrication
system.
2. Measure:
• Piston pin outside diameter “a”
Out of specification  Replace the piston
pin.
3. Measure:
• Piston pin bore inside diameter “b”
Out of specification  Replace the piston.
EAS1SM9229
INSTALLING THE PISTON AND CYLINDER
1. Install:
• Oil ring expander “1”
• Lower oil ring rail “2”
• Upper oil ring rail “3”
• Top ring “4”
TIP
Be sure to install the piston ring so that the
manufacturer’s marks or numbers face up.
2. Install:
• Piston “1”
• Piston pin “2”
• Piston pin clip “3”
Piston ring
Top ring
End gap (installed)
0.15–0.25 mm (0.0059–0.0098 in)
Limit
0.50 mm (0.0197 in)
Oil ring
End gap (installed)
0.10–0.35 mm (0.0039–0.0138 in)
Piston pin outside diameter
15.991–16.000 mm (0.6296–
0.6299 in)
Limit
15.971 mm (0.6288 in)
Piston pin bore inside diameter
16.002–16.013 mm (0.6300–
0.6304 in)
Limit
16.043 mm (0.6316 in)
b
4
New

Yamaha YZ250F 2016 Specifications

General

Displacement	250cc
Bore x Stroke	77.0mm x 53.6mm
Compression Ratio	13.5:1
Ignition	TCI
Transmission	5-speed
Final Drive	Chain
Suspension Rear	KYB® single shock; fully adjustable, 12.4-in travel
Brakes Front	Hydraulic single disc brake, 250mm
Brakes Rear	Hydraulic single disc brake, 245mm
Tires Front	80/100-21
Tires Rear	100/90-19
Length	85.6 in
Width	32.5 in
Seat Height	38.0 in
Rake (Caster Angle)	27.3°
Ground Clearance	12.8 in
Fuel Capacity	2.0 gal
Engine Type	Liquid-cooled, DOHC, 4-stroke, 4-valve
Fuel Delivery	Yamaha Fuel Injection (YFI), Keihin® 44mm
Suspension Front	KYB® Speed-Sensitive System, inverted fork; fully adjustable, 12.2-in travel