Yamaha 25BMH, Service Manual

Page: 248 / 446

CRANKSHAFT AND CYLINDER BODY
POWR
5-32
E
A: 15 mm (0.59 in) below the cylinder top
B: 25 mm (0.98 in) above the exhaust port
C: 100 mm (3.94 in) below the scavenging port
CHECKING THE PISTON
1. Check:
• Piston wall
Wear/scratch/damage
→
Replace.
2. Check:
• Piston head
• Piston ring groove
Carbon deposits
→
Clean.
CAUTION:
Take care not to scratch or cut the alumi-
num surface.
S S S Stttta a a an n n nd d d da a a arrrrd d d d W W W Wea ea ea ear r r r li li li lim m m miiiit t t t
C C C C y y y y llll iiii n d n d n d n d e e e e rrrr
bo bo bo borrrre e e e
d d d d iiii a a a a m m m m e e e e tttt e e e e rrrr
“ “ “ “D D D D” ” ” ”
7 7 7 72 2 2 2....0 0 0 00 0 0 0 ----7 7 7 72 2 2 2....02 02 02 02 mm mm mm mm
(((( 2 2 2 2 .... 8 3 8 3 8 3 8 3 4 4 4 4 6 6 6 6 – – – – 2 2 2 2 .... 8 3 8 3 8 3 8 3 5 5 5 5 4 4 4 4
iiiin n n n))))
72 72 72 72....1 1 1 10 0 0 0 mm mm mm mm
((((2 2 2 2....8 8 8 8386 386 386 386 iiiin n n n))))
T T T Ta a a ap p p pe e e er r r r li li li lim m m miiiit t t t
“ “ “ “T T T T” ” ” ”
– – – –
0 0 0 0....0 0 0 08 8 8 8 mm mm mm mm
((((0 0 0 0....0 0 0 00 0 0 031 31 31 31 iiiin n n n))))
O O O Ou u u ut t t t o o o of f f f rrrroun oun oun ound d d d
li li li lim m m miiiit t t t “ “ “ “R R R R” ” ” ”
– – – –
0 0 0 0....0 0 0 05 5 5 5 mm mm mm mm
((((0 0 0 0....0 0 0 00 0 0 020 20 20 20 iiiin n n n))))
D D D D = = = = M M M Ma a a ax x x xiiiim m m mu u u um m m m D D D D1 1 1 1, , , , D D D D2 2 2 2, , , , D D D D3 3 3 3, , , , D D D D4 4 4 4, , , , D D D D5 5 5 5 o o o or r r r D D D D6 6 6 6
T
T T
T =
= =
= ((((M
M M
Max
ax ax
axiiiim
m m
mu
u u
um
m m
m D
D D
D1
1 1
1 o
o o
or
r r
r D
D D
D2
2 2
2)
) )
) –
– –
– ((((M
M M
Miiiin
n n
niiiim
m m
mu
u u
um
m m
m D
D D
D5
5 5
5 o
o o
or
r r
r D
D D
D6
6 6
6))))
R R R R = = = = M M M Max ax ax axiiiim m m mu u u um m m m ((((D D D D1 1 1 1 – – – – D D D D2 2 2 2) ) ) ) o o o or r r r ((((D D D D3 3 3 3 – – – – D D D D4 4 4 4) ) ) ) o o o or r r r ((((D D D D5 5 5 5 – –– –
D D D D6 6 6 6))))