Yamaha MZ250 2012 Supplementary Service Manual page 4

HOW TO USE THIS MANUAL
This manual is intended as a handy, easy-to-read reference book for the mechanic.
Comprehensive explanations of all installation, removal, disassembly, assembly, repair and check
procedures are laid out with the individual steps in sequential order.
9 The manual is divided into chapters and each chapter is divided into sections. The current sec-
tion title is shown at the top of each page 1.
9 Sub-section titles appear in smaller print than the section title 2.
9 To help identify parts and clarify procedure steps, there are exploded diagrams at the start of
each removal and disassembly section 3.
9 Numbers are given in the order of the jobs in the exploded diagram. A number indicates a dis-
assembly step 4.
9 Symbols indicate parts to be lubricated or replaced 5.
Refer to "ILLUSTRATED SYMBOLS".
9 A job instruction chart accompanies the exploded diagram, providing the order of jobs, names of
parts, notes in jobs, etc. 6.
9 Jobs requiring more information (such as special tools and technical data) are described
sequentially 7.
CYLINDER HEAD COVER, CYLINDER HEAD
CYLINDER HEAD COVER, CYLINDER HEAD
4
6
3
5
11 Nm (1.1m · kgf, 8.0 ft · lbf)
2.3 Nm (0.23m · kgf, 1.7 ft · lbf)
6
Order Job/Parts to remove
Removing the cylinder head cover
and cylinder head
Fuel tank
Muffler
Air filter
Carburetor
Flywheel cover
1 Spark plug cap
2 Spark plug
3 Breather hose
4 Cylinder head cover
5 Cylinder head cover gasket
6 Cylinder air shroud
7 Locknut
8 Adjuster
9 Screw
chap03.indd 21
1
ENG
3
5
4
11 Nm (1.1m · kgf, 8.0 ft · lbf)
1
20 Nm (2.0 m · kgf, 14 ft · lbf)
2
9
9
7 8
1st 12 Nm (1.2 m · kgf, 8.7 ft · lbf)
7 Nm (0.7 m · kgf, 5.1 ft · lbf)
2nd 50 Nm (5.0 m · kgf, 36 ft · lbf)
Q'ty Remarks
Remove the parts in the order listed
below.
Refer to "FUEL TANK, CANISTER" on 3-5.
Refer to "MUFFLER" on 3-7.
Refer to "AIR FILTER" on 3-3.
Refer to "CARBURETOR" on 4-1.
Refer to "FLYWHEEL" on 3-13.
1
1
1
1
1
1
2
2
2
3-21
CYLINDER HEAD COVER, CYLINDER HEAD
7 8
2012/09/14 10:45:52 chap03.indd 23
ENG
CHECKING THE ROCKER ARM
1. Check:
9 Rocker arm
Wear/damage/cracks → Replace.
CHECKING THE PUSH ROD
1. Check:
9 Push rod runout
Runout limit:
Refer to "SPECIFICATIONS" in
the Supplementary service
manual.
Out of specifications → Replace.
CHECKING THE CYLINDER HEAD
1. Check:
9 Cylinder head combustion chamber
Check the combustion chamber for car-
bon deposits.
Any carbon deposits → Eliminate.
TIP
Be sure not to damage the contact surface of
the cylinder.
2. Check:
9 Cylinder head
Cracks/damage around the hole of
spark plug → Replace.
3-23
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2
7
10:45:52