Page 51 of 364

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-3
BASE ENGINE
M2112001000864
CYLINDER HEAD
AK305050AB
Spark plug guide
Intake
side
Exhaust
side
Valve guide
The cylinder head is made of aluminu m alloy , which
is light
we ight a nd ha s an excelle nt co oling ef ficiency .
The pentroof type comb ustion chamb e r has a sp a r k
plug in the
cent er . The valve an gle is relatively small,
contributing to size redu
ctio n.
The int a ke an d exhaust port s a r e arrang ed in a
cross-flow construction.
Ea ch cylinde r has a p a ir of
int
a ke port s on one side and a p a ir of e x hau st po rt s
on the
other side .
Each o f the int a ke a nd exhaust ca msh a f t s is sup-
ported by 5 bearin gs. On ea ch camshaf t, th e thrust
load
is suppo rted by No. 1 b earin g. The No . 1 bea r
-
ings for the int a ke and exha ust camshaf t s ha ve a
common bearing
ca p.
VALV E S E AT
AK305052
d
AB
d
DD h
h
Intake
Exhaust
Sintered
alloy valve seat
ItemIntakeExhaust
D (Outer
diameter) mm31.528
d (Inner
diameter) mm2622
h (height) mm6.67.3
Page 52 of 364
BASE ENGINE
ENGINE MECHANICAL <4A9>11A-4
VA LV E G U I D E
AK305053
d
AB
Dh
The in
t a ke an d exhaust valves use the same -design
valve gu
ide.
ItemIntake
D (Outer diameter) mm10.5
d (Inner diameter) mm4.5
h (height) mm34.5
CYLINDER HEAD GASKET
AK305054AB
Water hole
Oil hole
Water hole
Th e met a l g a sket having he at resist ance, sea l ability
and low cost is use
d for th e cylin der hea d gasket .
CYLINDER HEAD COVER
AK402398AC
Cylinder head cover
A resin cylin der hea d co ver is used fo r the cylinder head.
Page 53 of 364
BASE ENGINE
ENGINE MECHANICAL <4A9>11A-5
CYLINDER BLOCK
AK402339AC
Front view
Right side view
Under view
Top view
Rear view
Left side view
Thermostat case installation positionOil filter bracket installation position Front
Front Front Front
Nipple
The cylinder b
l ock is ma de of ligh twe i ght aluminum
allo
y .
The crankshaf t jo urnal is supp orted b y 5 b earing s .
The crankshaf
t thru st load is supporte d by No . 4
bearin
g.
The water jacket is of a full-siamese de sig n .
A nipple is p r ovid ed at the fr o n t of the block to su pply
engin
e oil onto the timin g ch ain.
ItemDimension
Overall height mm280
Overall length mm375.1
Top face to crankshaft
center mm205
Crankshaft center to
bottom face mm75
Bore mm75
Bore pitch mm83
Stroke mm84.8
Page 54 of 364

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-6
REAR OIL SEAL CASE
AK305061AB
AA A-A
The rea
r oil seal ca se is a sheet -met al wor k . The
case is
inst alled with sealant ap plie d onto th e mou n t
-
ing face to prevent oil leaka ge.
PISTON
AK403222
AB
Front mark
Piston pin offset
The pisto n is made of spec ial a l uminu m all o y . W e ig ht
reduction
is a c hieved by minimizin g the o v erall
heigh
t while maximizing th e recess on bo th end s of
the piston
pin.
The center o f the p i sto n pin hole is of fset by 0.5 mm
from t
he ce nter of the piston towards the th rust side .
The piston skirt ha s a streak finish to enha nce oil
retention an
d anti-seizin g prope rty .
ItemDimension
Base diameter mm75
Pin diameter mm18
Overall height mm46.04
PISTON PIN
AK305064
d
AB
D
h
The piston pin is o f a semi-floating type, p r ess-fitte d
into t
he co nnecting rod small end wh ile cap able of
floating re
lative to the piston .
ItemDimension
D (Outer diameter) mm18
d (Inner diameter) mm11
h (Overall length) mm50
Page 67 of 364

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-19
BASE ENGINE
M2112001000875
CYLINDER HEAD
AK305050AB
Spark plug guide
Intake
side
Exhaust
side
Valve guide
The cylinder head is made of aluminu m alloy , which
is light
we ight a nd ha s an excelle nt co oling ef ficiency .
The pentroof type comb ustion chamb e r has a sp a r k
plug in the
cent er . The valve an gle is relatively small,
contributing to size redu
ctio n.
The int a ke an d exhaust port s a r e arrang ed in a
cross-flow construction.
Ea ch cylinde r has a p a ir of
int
a ke port s on one side and a p a ir of e x hau st po rt s
on the
other side .
Each o f the int a ke a nd exhaust ca msh a f t s is sup-
ported by 5 bearin gs. On ea ch camshaf t, th e thrust
load
is suppo rted by No. 1 b earin g. The No . 1 bea r
-
ings for the int a ke and exha ust camshaf t s ha ve a
common bearing
ca p.
VALV E S E AT
AK305052
d
AB
d
DD h
h
Intake
Exhaust
Sintered
alloy valve seat
ItemIntakeExhaust
D (Outer
diameter) mm31.528
d (Inner
diameter) mm2622
h (height) mm6.67.3
Page 68 of 364
BASE ENGINE
ENGINE MECHANICAL <4A9>11A-20
VA LV E G U I D E
AK305053
d
AB
Dh
The in
t a ke an d exhaust valves use the same -design
valve gu
ide.
ItemIntake
D (Outer diameter) mm10.5
d (Inner diameter) mm4.5
h (height) mm34.5
CYLINDER HEAD GASKET
AK305054AB
Water hole
Oil hole
Water hole
Th e met a l g a sket having he at resist ance, sea l ability
and low cost is use
d for th e cylin der hea d gasket .
CYLINDER HEAD COVER
AK402398AC
Cylinder head cover
A resin cylin der hea d co ver is used fo r the cylinder head.
Page 69 of 364
BASE ENGINE
ENGINE MECHANICAL <4A9>11A-21
CYLINDER BLOCK
AK402339AC
Front view
Right side view
Under view
Top view
Rear view
Left side view
Thermostat case installation positionOil filter bracket installation position Front
Front Front Front
Nipple
The cylinder b
l ock is ma de of ligh twe i ght aluminum
allo
y .
The crankshaf t jo urnal is supp orted b y 5 b earing s .
The crankshaf
t thru st load is supporte d by No . 4
bearin
g.
The water jacket is of a full-siamese de sig n .
A nipple is p r ovid ed at the fr o n t of the block to su pply
engin
e oil onto the timin g ch ain.
ItemDimension
Overall height mm280
Overall length mm375.1
Top face to crankshaft
center mm205
Crankshaft center to
bottom face mm75
Bore mm75
Bore pitch mm83
Stroke mm84.8
Page 70 of 364

BASE ENGINE
ENGINE MECHANICAL <4A9>11A-22
REAR OIL SEAL CASE
AK305061AB
AA A-A
The rea
r oil seal ca se is a sheet -met al wor k . The
case is
inst alled with sealant ap plie d onto th e mou n t
-
ing face to prevent oil leaka ge.
PISTON
AK403222
AB
Front mark
Piston pin offset
The pisto n is made of spec ial a l uminu m all o y . W e ig ht
reduction
is a c hieved by minimizin g the o v erall
heigh
t while maximizing th e recess on bo th end s of
the piston
pin.
The center o f the p i sto n pin hole is of fset by 0.5 mm
from t
he ce nter of the piston towards the th rust side .
The piston skirt ha s a streak finish to enha nce oil
retention an
d anti-seizin g prope rty .
ItemDimension
Base diameter mm75
Pin diameter mm18
Overall height mm46.04
PISTON PIN
AK305064
d
AB
D
h
The piston pin is o f a semi-floating type, p r ess-fitte d
into t
he co nnecting rod small end wh ile cap able of
floating re
lative to the piston .
ItemDimension
D (Outer diameter) mm18
d (Inner diameter) mm11
h (Overall length) mm50