5
. CYLINDER/PISTON
2
BR & M2 250 ENGINE
SERVICE INFORMATION
GENERAL INSTRUCTIONS
•
The cylinder and piston can be serviced with the engine installed in the frame.
•
When installing the cylinder, use a new cylinder gasket and make sure that the dowel pins are correctly
installed.
•
After disassembly, clean the removed parts and dry them with compressed air before inspection.
SPECIFICATIONS
Standard (mm)
Service Limit (mm)
Item
SH50
SH50
I.D.
72.7500
∼
72.7015
72.80
Warpage
0.01
0.05
Cylindricity
0.01
0.05
True roundness
0.01
0.05
Ring-to-groove
top
0.2
0.09
clearance
Second
0.015
∼
0.050
0.09
top
0.1
∼
0.25
0.50
Piston,
Ring end gap
Second
0.15
∼
0.30
0.50
piston ring
Oil side rail
0.25
∼
0.7
Piston O.D.
72.67
∼
72.69
72.6
Piston O.D. measuring position
9mm from bottom of skirt
9mm from bottom of skirt
.
Piston-to-cylinder clearance
0.010
∼
0.040
0.01
Piston pin hole I.D.
17.002
∼
17.008
17.04
Piston pin O.D
16.994
∼
17.000
16.96
Piston-to-piston pin clearance
0.002
∼
0.014
0.02
Connecting rod small end I.D. bore
17.016
∼
17.034
17.06
TROUBLESHOOTING
•
When hard starting or poor performance at low speed occurs, check the crankcase breather for white
smoke. If white smoke is found, it means that the piston rings are worn, stuck or broken.
Compression too low or uneven
compression
Excessive smoke from exhaust muffler
•
Worn or damaged cylinder and piston rings
•
Worn or damaged piston rings
•
Worn, stuck or broken piston rings
•
Worn or damaged cylinder and piston
Compression too high
Abnormal noisy piston
•
Excessive carbon build-up in combustion
•
Worn cylinder, piston and piston rings
chamber or on piston head
•
Worn piston pin hole and piston pin
•
Incorrectly installed piston
Cylinder
Summary of Contents for Bug Rider BR-250
Page 1: ...BR 250 BR 250SS M2 250 SERVICE MANUAL Manufactured by PGO of Motive Power Industry Co Ltd...
Page 34: ...4 CYLINDER HEAD VALVES 1 BR M2 250 ENGINE SCHEMATIC DRAWING...
Page 46: ...5 CYLINDER PISTON 1 BR M2 250 ENGINE SCHEMATIC DRAWING...
Page 55: ...6 DRIVE AND DRIVEN PULLEYS KICK STARTER 1 BR M2 250 ENGINE SCHEMATIC DRAWING...
Page 71: ...7 FINAL REDUCTION 1 BR M2 250 ENGINE SCHEMATIC DRAWING...
Page 82: ...8 CARBURETOR BR M2 250 ENGINE...
Page 90: ...9 A C GENERATOR STARTER CLUTCH 1 BR M2 250 ENGINE SCHEMATIC DRAWING...
Page 97: ...10 CRANKCASE CRANKSHAFT 1 BR M2 250 ENGINE SCHEMATIC DRAWING...
Page 103: ...10 CRANKCASE CRANKSHAFT 7 BR M2 250 ENGINE Torque 7 8 11 8N m Cam Chain Tensioner Slipper Bolt...
Page 105: ...11 COOLING SYSTEM 1 BR M2 250 ENGINE SCHEMATIC DRAWING...