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BP-002 · Four-stroke engine
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A
A
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C
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D
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F
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345
168
s=0
26
24
23
14
28
17
13
12
1
25
20
19
29
16
18
C
AXIAL SECTION
THROUGH CYLINDER AND VALVE AXES · SCALE 1:1
15
27
DETAIL C
CHAMBER, SEATS AND PLUG · 2:1
8
9
10
11
7
6
DETAIL B
RING PACK, RIDING WITH THE PISTON · 2:1
0.5
1
2
5
10
20
50
100
0
25
50
75
100
125
150
CYLINDER VOLUME V, cm³
p, bar (LOG)
TDC
BDC
DIAGRAM 1 · P–V
ACCENT: THIS CYCLE · THIN: THE COMPUTED CYCLE
1 INTAKE
2 COMP.
3 POWER
4 EXHAUST
0
2
4
6
8
0
180
360
540
720
CRANK ANGLE φ, °
LIFT, mm
IN
EX
IGN
DIAGRAM 2 · VALVE LIFT
FROM THE CAM PROFILES · DASHED: EXHAUST
NOTES
1. BORE × STROKE 56.5 × 49.5; SWEPT 124.1 cm³.
2. CLEARANCE 15.1 cm³; CR 9.23 : 1.
3. CYCLE AT 6000 rpm, FULL THROTTLE,
4. SHOWN 400× SLOWER. PEAK 58 bar AT 13° ATDC.
5. IMEP 11 bar · 6.8 kW INDICATED.
6. IVO 18° BTDC · IVC 54° ABDC.
7. EVO 56° BBDC · EVC 12° ATDC.
8. IGNITION 25° BTDC. CAMS AT ½ CRANK.
ITEM
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DESCRIPTION
CRANKCASE
FLYWHEEL WEB, COUNTERWEIGHTED
CRANKPIN Ø22
NEEDLE CAGE K 22×28×17
CONNECTING ROD, 98 C/C
GUDGEON PIN Ø14×Ø9×44
PISTON Ø56.5
TOP RING 56.5×1.0
SECOND RING 56.5×1.2, TAPER
OIL RING 56.5×2.0, 3-PIECE
CYLINDER LINER Ø56.5×Ø64
CYLINDER BARREL, FINNED
HEAD GASKET 0.8
CYLINDER HEAD, FINNED
VALVE SEAT INSERT
VALVE GUIDE Ø5.5
INLET VALVE Ø22
EXHAUST VALVE Ø18.5
VALVE STEM SEAL
VALVE SPRING, 6 TURNS
SPRING RETAINER
VALVE COLLET, PAIR
BUCKET TAPPET Ø26 + SHIM
INLET CAMSHAFT
EXHAUST CAMSHAFT
CAM COVER
SPARK PLUG M10×1, 12.7 REACH
INLET MANIFOLD
EXHAUST PIPE Ø27×1.5
MATERIAL
EN AC-46000 (AlSi9Cu3)
42CrMo4
20MnCr5, CASE HARD.
100Cr6
42CrMo4
17Cr3, CASE HARD.
AlSi12CuNiMg
STEEL, NITRIDED
EN-GJL-250
STEEL
EN-GJL-250
EN AC-46000
MLS STEEL
EN AC-42100 T6
SINTERED Fe-Cu
CuNi2Si
X45CrSi9-3
X53CrMnNiN21-9
FKM
EN 10270-2 Ø2.8
42CrMo4
C15
16MnCr5
EN-GJL CHILLED
EN-GJL CHILLED
EN AC-46000
BOUGHT OUT
EN AC-46000
X5CrNi18-10
QTY
1
2
1
1
1
1
1
1
1
1
1
1
1
1
2
2
1
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2
2
2
2
1
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1
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1
1
TITLE
125 cc FOUR-STROKE · SECTION
DWG NO
BP-002
SCALE
1:1
SIZE
A2
SHEET
1 / 1
DRAWN
CLAUDE
DATE
2026-10-15
MATERIAL
SEE PARTS LIST
GENERAL TOL.
ISO 2768-m
UNITS
mm · bar abs · °
LIVE · DRAG THE CRANK · ← → TURN · SPACE RUNS · S SLOW
Drag the crank ·
←
→
turn ·
Space
run ·
S
slow
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