8.

CYLINDER/PISTON

SYSTEM DIAGRAM

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Mo O
IL

Mo O
IL
Mo O
IL

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CYLINDER/PISTON

System Diagram 8-0 Piston Ring Installation 8-7

Service Information 8-1 Piston Installation 8-9
Specification/Torque Values 8-1 Cylinder Installation 8-10
Special Tools/Troubleshooting 8-2 Cam Chain Tensioner
Cylinder Removal 8-3 Lifter Removal 8-11
Piston Removal 8-4 Cam Chain Tensioner
Piston/Piston Ring Inspection 8-5 Lifter Installation 8-12

SERVICE INFORMATION
GENERAL
• Cylinder and piston can be serviced with the engine installed in the frame.
• Be careful not to damage the mating surfaces by using a screwdriver when removing the cylinder. Do not strike the cylinder too
hard during removal, even with a rubber or plastic hammer, to prevent the possibility of damage to the fins.
• When installing piston pin apply molybdenum disulfide oil to its whole surface.
• Take care not to damage the cylinder wall and piston.

SPECIFICATIONS
CYLINDER/PISTON
ITEM STANDARD SERVICE LIMIT
I.D 65.5-66.51 mm 66.58 mm
Ovality - 0.10 mm
Cylinder
Taper - 0.10 mm
Warpage - 0.10 mm
Piston O.D 66.4575-66.4725 mm 66.39 mm
Piston pin hole I.D 15.005-15.01 mm 15.04 mm
Piston pin O.D 14.994-15.000 mm 14.96 mm
.
Piston-to-piston pin clearance 0.005-0.016 mm 0.07 mm
Connecting. rod small end I.D 15.010-15.028 mm 15.06 mm
Cylinder-to-piston clearance 0.010-0.030 mm 0.10 mm
Piston
Connecting. rod-to-piston clearance 0.010-0.034 mm 0.10 mm
Piston ring-to-groove Top 0.03-0.060 mm 0.10 mm
clearance Second 0.03-0.060 mm 0.10 mm
Top 0.15-0.3 mm 0.55 mm
Piston ring end gap Second 0.3-0.4 mm 0.75 mm
Oil (side rail) 0.20-0.70 mm 1.10 mm

TORQUE VALUES

STUD BOLT : 1.1 kgf-m

For other nuts, bolts, fasteners etc. refer to standard torque values (SECTION-1).

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 CYLINDER/PISTON

SPECIAL TOOLS

PISTON SLIDE BASE

PART NO: 070 HH 198 027

TROUBLESHOOTING
Compression too low, hard to start or
poor performance at low speed
• Worn, stuck or broken piston rings
• Worn or damaged cylinder or piston
• Leaking cylinder head gasket

Excessive smoke
• Worn cylinder or piston rings
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• Improper installation of piston rings
• Scored or scratched piston or cylinder wall

Excessive noise (piston)

• Worn cylinder and piston
• Worn piston pin and piston pin hole
• Worn connecting rod small end

Overheating, knocking/compression too high

• Excessive carbon deposit on piston or combustion chamber

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CYLINDER/PISTON
CAM CHAIN SPROCKET
CYLINDER
REMOVAL
Remove the cylinder head (page 7-4).
Remove the dowel pins and gasket (page 7-8).
Remove the cam chain guide and cam sprocket.

CAM CHAIN GUIDE

CYLINDER
Lift the cylinder and remove it, being careful not to damage
the piston with the studs.
Clean the top of the cylinder throughly.
NOTE
Be careful not to damage the mating surfaces by using a
screwdriver when splitting the cylinder from the crankcase.

DOWEL PINS
Remove the dowel pins and gasket.

GASKET

STUD REPLACEMENT
Remove the studs from the crankcase.
Install the new studs into the crankcase embedded till 113.4- 115.4 mm
incomplete threads.
TORQUE
STUD BOLT: 1.1 kgf-m
After installing the studs check that the length from the head
to the crankcase surface is within specification.
STUDS
(EMBEDDED TILL INCOMPLETE THREADS)

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 CYLINDER/PISTON
CYLINDER
CYLINDER
WEAR
INSPECTION
Inspect the cylinder wall for scoring and wear.
Measure and record the cylinder I.D at three levels in both the
X and Y axis. Take the maximum reading to determine the
cylinder wear.
SERVICE LIMIT
CYLINDER I.D: 66.58 mm

Calculate the cylinder for taper and ovality at three levels in

an X and Y axis. Take the maximum reading to determine the IN EX
ovality.
TOP
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SERVICE LIMIT
TAPER: 0.10 mm
OVALITY: 0.10 mm MIDDLE
The cylinder must be rebored and an oversize piston fitted if
the service limit is exceeded.
The following oversize piston are available: BOTTOM
0.25 mm- 1.00 mm
The cylinder must be rebored so that the clearance for
oversize piston is 0.010- 0.030 mm.

Check the cylinder for warpage by placing a straight edge

and a feeler gauge across the studs and bolt holes as shown.
SERVICE LIMIT
CYLINDER WARPAGE: 0.10 mm

PISTON PIN CLIP

PISTON
REMOVAL
Remove the piston pin clip using nose plier.
NOTE
Place a clean shop towel over the crankcase to prevent the
possibility of the piston pin clip falling into the crankcase.

NOSE PLIER

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CYLINDER/PISTON
BLUNT SHAFT
Remove the piston pin out by driving it with a blunt shaft.
CAUTION
• Do not damage or scratch the piston
• Do not apply side force to the connecting rod.

PISTON PISTON PIN

PISTON
Inspect the piston rings for movement by pressing the rings.
The rings should be able to move in its groove without
catching.

PISTON RING
PISTON
Spread each piston ring and remove it by lifting it up at a
point opposite the gap.
CAUTION
• Do not damage the piston ring by spreading the ends
too far.
• Be careful not to damage the piston during the piston
ring removal.

PISTON RING
PISTON RING PISTON
PISTON/PISTON RING
INSPECTION
NOTE
• Clean carbon deposits from the piston.
ABNORMAL
• Clean carbon deposits from the piston ring grooves with WEAR
a ring that will be discarded. Never use a wire brush; it
will damage the grooves.
Inspect the piston for cracks or other damage.
Inspect the ring grooves for excessive wear and carbon build-
up.
PISTON RING

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 CYLINDER/PISTON

Measure piston O.D at 10 mm from the bottom, and 900 to

the piston pin hole.
SERVICE LIMIT
PISTON O.D: 66.39 mm
Calculate the cylinder- to- piston clearance. Take the maximum
calculate the cylinder-to-piston clearance reading to
determine the clearance.
SERVICE LIMIT
CYLINDER- TO- PISTON CLEARANCE: 0.10 mm O.D

PISTON
Measure each piston pin hole I.D. in an X and Y axis.
Take the maximum reading to determine I.D.
SERVICE LIMIT Y
X

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PISTON PIN HOLE I.D: 15.04 mm

I.D

Measure the piston pin O.D. at three points.

SERVICE LIMIT
PISTON PIN O.D: 14.96 mm
Calculate the piston-to-piston pin clearance. O.D
SERVICE LIMIT
PISTON-TO-PISTON PIN CLEARANCE: 0.07 mm

PISTON PIN
CONNECTING ROD
Measure the connecting rod small end I.D.
SERVICE LIMIT
CONNECTING ROD SMALL END I.D: 15.06 mm
Calculate the connecting rod small end-to-piston pin
clearance.
I.D
SERVICE LIMIT
CONNECTING ROD SMALL END-PISTON PIN
CLEARANCE: 0.10 mm

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CYLINDER/PISTON

Using a piston, push the ring securely into the cylinder and
measure the piston ring end gap using a feeler gauge.
SERVICE LIMIT
TOP RING END GAP: 0.55 mm
SECOND RING END GAP: 0.75 mm
OIL RING END GAP: 1.10 mm

PISTON RING

PISTON RING
Inspect the piston rings and replace them if they are worn.
NOTE
Always replace the piston rings as a set.
Reinstall the piston rings into the piston grooves.
Push in until the outer surface of the piston ring is nearly
flushed with the piston and measure the clearance using a
feeler gauge.
SERVICE LIMIT
TOP: 0.10 mm
SECOND: 0.10 mm

PISTON
PISTON RING INSTALLATION
Clean the piston heads, ring land and skirt.
Carefully install the piston rings onto the piston with their
marking facing up.
CAUTION
• Do not damage the piston ring by spreading the ends too
far.
• Be careful not to damage the piston when the piston ring
installation.
NOTE
• Do not confuse the top and second rings. PISTON RING
• After installing the rings they should rotate freely, without
sticking.
• Space the ring end gaps 120° apart.

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 CYLINDER/PISTON

MARK

2 TOP
TOP 1

120°

TOP RING 120° 8

120° 120°
SECOND RING
120°
SIDE RAIL

SPACER 120°
0
45
SIDE RAIL

0
45

TOP RING
SECOND RING
OIL RING

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CYLINDER/PISTON

PISTON
INSTALLATION
NOTE
When cleaning the cylinder mating surface, place a shop
towel over the crankcase opening to prevent dirt entry into
the engine.
Clean any gasket material from the cylinder mating surface
of the crankcase.

MATING SURFACE
BLUNT SHAFT
Apply molybdenum oil solution to the piston pin outer
surfaces.
Install the piston with its “IN” mark facing the intake side.
Install the piston pin.

Mo OIL
PISTON PISTON PIN
PISTON PIN CLIP
Install new piston pin clips.
CAUTION
Always use new piston pin clips . Reinstalling used piston pin
clips may lead to serious engine damage.

NOSE PLIER
CLIP END GAP
NOTE
• Place a shop towel over the crankcase opening to
prevent piston pin clips from the falling into the
crankcase.
• Set the piston pin clip in the groove properly.
• Do not align the clip’s end gap with the piston cut-out.

PISTON CUT OUT

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DOWEL PINS
CYLINDER
INSTALLATION
Install the dowel pins and a new gasket.
NOTE
• When cleaning the cylinder mating surface, place a
shop towel over the crankcase opening to prevent dirt
entry into the engine.
• Do not reuse the gasket, replace with new one.

CAUTION
GASKET
• Be careful not to damage the piston rings and cylinder
wall. CYLINDER CYLINDER WALL
• Be careful not to jam the piston rings to the cutaway of the
cylinder sleeve.
Apply clean engine oil to the cylinder wall, piston outer
8
surface and piston rings.
Place piston slide base under the piston.
Install the cylinder over the piston compressing the piston
rings with your fingers.
Route the cam chain through the cylinder.

PISTON SLIDE BASE PISTON SLIDE BASE PISTON/PISTON RING

PART NO: 070 HH 198 027 CAM CHAIN GUIDE
Insert the cam chain guide into the cylinder and crankcase
groove.

GROOVE
CAM CHAIN SPROCKET
Temporarily, install the cam sprocket on the cam chain.
Install the gasket and dowel pins (page 7-17).
Install the cylinder head (page 7-17).

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O-RING
CAM CHAIN TENSIONER LIFTER
REMOVAL
Remove the tensioner pan screw and O-ring.
NOTE
Always use impact drive to remove the pan screw.

PAN SCREW
TENSIONER LIFTER BOLTS
Turn the tensioner shaft clockwise with the stopper tool to
retract the tensioner, then insert the stopper fully to hold the
tensioner in the fully retracted position.
Remove the two mounting bolts.

STOPPER TOOL
GASKET
Remove the cam chain tensioner lifter and gasket.

TENSIONER LIFTER

INSPECTION
Check the lifter operation:
- The tensioner shaft should not go into the body when it is
pushed.
- When it is turned clockwise with a stopper tool
the tensioner lifter shaft should be pulled into the body .
- The shaft should spring out of the body as soon as the
stopper tool is released.

TENSIONER LIFTER

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TENSIONER LIFTER
CAM CHAIN TENSIONER LIFTER
INSTALLATION
Turn the tensioner lifter shaft clockwise with the stopper tool
to retract the tensioner lifter, then insert the stopper fully to
hold the tensioner lifter in the retracted position.

STOPPER TOOL
GASKET
Install the cam chain tensioner lifter along with a new gasket.
NOTE
Never assemble the tensioner lifter to the engine with the 8
tension condition, as it may cause cam chain noise/wear.

CAM CHAIN TENSIONER LIFTER

TENSIONER LIFTER BOLTS
Install the mounting bolts and tighten them.
Remove the stopper tool from the tensioner lifter.

STOPPER TOOL
O-RING
Apply clean engine oil to a new O-ring and install it to the
lifter.
Install the tensioner lifter pan screw and tighten it.
NOTE
Always use impact drive to install the pan screw.

TENSIONER LIFTER PAN SCREW

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MEMO