Troubleshooting; Service Information - Honda CBR125R Owner's Manual

SERVICE INFORMATION

GENERAL
• This section covers maintenance of the cylinder and piston. To service these parts, the engine must be removed from
the frame.
• Take care not to damage the cylinder wall and piston.
• Be careful not to damage the mating surfaces when removing the cylinder. Do not strike the cylinder too hard during
removal.
• Camshaft and rocker arm lubricating oil is fed through an oil passage in the cylinder. Clean the oil passage before
installing cylinder.
SPECIFICATIONS
Cylinder I.D.
Out-of-round
Taper
Warpage
Piston, Piston O.D. at 6.5 (0.26) from bottom
piston pin,
Piston pin hole I.D.
piston ring
Piston pin O.D.
Piston-to-piston pin clearance
Piston ring end gap
Piston ring-to-ring
groove clearance
Cylinder-to-piston clearance
Connecting rod small end I.D.
Connecting rod-to-piston pin clearance
TORQUE VALUE
Cylinder stud bolt

TROUBLESHOOTING

Compression too low, hard starting or poor performance at low speed
• Leaking or damaged cylinder head gasket
• Worn, stuck or broken piston rings
• Worn or damaged cylinder and piston
• Loose spark plug
Compression too high, overheating or knocking
• Excessive carbon built-up on piston or combustion chamber
Excessive smoke
• Faulty cylinder, piston and piston rings
• Improper installation of piston rings
• Scored or scratched piston or cylinder wall
Abnormal noise (piston)
• Worn piston pin or piston pin hole
• Faulty cylinder, piston or piston ring
• Worn connecting rod small end
ITEM
Top
Second
Oil (side rail)
Top
Second
STANDARD
58.000 – 58.010 (2.2835 – 2.2839)
–
–
–
57.970 – 57.990 (2.2823 – 2.2831)
13.002 – 13.008 (0.5119 – 0.5121)
12.994 – 13.000 (0.5116 – 0.5118)
0.002 – 0.014 (0.0001 – 0.0006)
0.10 – 0.25 (0.004 – 0.010)
0.35 – 0.50 (0.014 – 0.020)
0.20 – 0.70 (0.008 – 0.028)
0.045 – 0.075 (0.0018 – 0.0030)
0.015 – 0.050 (0.0006 – 0.0020)
0.010 – 0.040 (0.0004 – 0.0016)
13.016 – 13.034 (0.5124 – 0.5131)
0.016 – 0.040 (0.0006 – 0.0016)
– See page 9-8
CYLINDER/PISTON
Unit: mm (in)
SERVICE LIMIT
58.05 (2.285)
0.010 (0.0004)
0.010 (0.0004)
0.05 (0.002)
56.67 (2.231)
13.045 (0.5136)
12.70 (0.500)
0.08 (0.003)
0.40 (0.016)
0.70 (0.028)
1.10 (0.043)
0.10 (0.004)
0.09 (0.004)
0.09 (0.004)
13.06 (0.514)
0.10 (0.004)
9-3