um UXPW125 User Manual

UXPW 125 ENGINE SERVICE MANUAL AND EFI DIAGNOSTIC
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5.2 Limits for service
Cylinder and Piston unit：mm
Item
S tandard value
Service Limit
Cylinder
Inner diameter of cylinder
Φ52.400～φ52.410
Φ52.5
Cylindricity
0.004
0.10
Flatness of cylinder face
0.03
0.10
Piston, Piston
Ring and
Piston Pin
Outer diameter of piston
Φ52.38～φ52.39
Φ52.3
Inner diameter of piston pin hole
φ14.002～φ14.008
φ14.04
Closure clearance of
piston ring
Top
0.1～0.25
0.35
Second
0.15-0.30
0.4
Oil ring
0.2～0.7
0.85
gap between piston
rings and piston rings
Top
0.02～0.06
0.10
Second
0.02～0.06
0.10
Piston/Cylinder Clearance
0.01～0.03
0.07
Outer diameter of piston pin
φ13.994～φ14
φ13.96
Clearance between piston pin and piston
pin hole
0.002～0.014
0.04
Small End of
Connecting
Rod
Inner diameter
φ14.015～φ14.028
φ14.06
Clearance between small end of
connecting rod and piston pin
0.015～0.03
0.10
Tightening torque of AB bolt: 11N.m
5.3 Troubleshooting
5.3.1. Cylinder pressure is too low or there is no cylinder pressure (performance at low speed is
not acceptable)
• Severely worn or broken piston ring
• Damaged or broken cylinder block or piston
5.3.2. Cylinder pressure is too high. Engine overheats.
• Too much carbon deposit on piston top
5.3.3. Engine oil is consumed significantly, and engine smokes heavily.
• Severely worn or broken cylinder block and piston
• Improper assembly of piston ring
5.3.4. Abnormal noise
• Improper assembly of piston
• Fit clearance is too large between piston and piston pin, and the cylinder block and
piston are severely worn.

um UXPW125 Specifications

General

Brand	um
Model	UXPW125
Category	Engine
Language	English