Yamaha yz250 2015, Owner'S Manual

Page: 83 / 174

4-19
CYLINDER HEAD, CYLINDER AND PISTON
INSTALLING THE PISTON RING
AND PISTON
1. Install:
• Piston ring "1"
• Take care not to scratch the piston
or damage the piston ring.
• Align the piston ring gap with the pin
"2".
• After installing the piston ring,
check the smooth movement of it.
2. Install:
• Gasket (cylinder) "1"
• Small end bearing "2"
• Dowel pin "3"
• Apply the engine oil onto the bear-
ing (crankshaft and connecting rod)
and connecting rod big end wash-
ers.
• Install the gasket with the seal print
side toward the crankcase.
3. Install:
• Piston "1"
• Piston pin "2"
• Piston pin clip "3"
• The arrow "a" on the piston dome
must point to exhaust side.
• Before installing the piston pin clip,
cover the crankcase with a clean
rag to prevent the piston pin clip
from falling into the crankcase cavi-
ty.
• Apply the engine oil on the piston
pin.
Do not allow the clip open ends to
meet the piston pin slot "b".
INSTALLING THE CYLINDER
HEAD AND CYLINDER
1. Apply:
• Engine oil
To piston "1", piston ring "2" and
cylinder surface.
2. Install:
• Cylinder "1"
Make sure the piston rings are
properly positioned. Install the cyl-
inder with one hand while com-
pressing the piston rings with the
other hand.
After installing, check the smooth
movement of the piston.
3. Install:
• Nut (cylinder) "1"
Tighten the nuts in stage, using a
crisscross pattern.
4. Install:
• Push rod "1"
• Bolt (push rod) "2"
• Insert the set pin "3" included in
owner's tool kit to install the bolt
(push rod).
• Do not forget to remove the set pin.
Be sure to use the set pin. If the set
pin is not used, the power valve
constituent parts will result in
damage.
Nut (cylinder):
42 Nm (4.2 m•kg, 30
ft•lb)
Bolt (push rod):
5 Nm (0.5 m•kg, 3.6
ft•lb)