GPX NC450 - Cylinder Block and Piston Service

Page
13
31
Cylinder block and piston repair
1. Maintenance Instructions
2. Disassembly of the cylinder
3. Cylinder inspection
4. Disassembly of the piston
5. Inspection of piston and piston ring
6. Installation of piston ring 7. Installation of piston
8. Installation of the cylinder
Maintenance notice
Notes :
● The cylinder head lubricating oil is supplied to the cylinder head through the small oil
hole next to the AB bolt on the left body of the engine. Before installing the cylinder,
make sure that the small oil hole next to the AB bolt on the left body is unobstructed.
Do not install the solid positioning pin of the cylinder block into the oil passage hole.
Maintenance parameters of each component
project
Standard value mm
Maintenance limit
mm
cylinder
Cylinder bore
φ94.5～φ94.52
φ94.528
Out of roundness
0.05
0.01
Cylinder surface flatness
0.03
0.05
piston
piston ring
live
plugged
Piston outside diameter
φ94.45～φ94.46
φ94.43
Piston pin hole inner diameter
φ20.001～φ20.006
φ20.015
Piston pin and piston pin hole clearance
0.001～0.012
0.025
Piston Ring Closed
Gap
Top
Ring/Second
Ring
0.2～0.35
0.5
oil ring
0.2～0.7
1.4
Piston ring and piston
ring groove clearance
top ring
0.03～0.07
0.08
second ring
0.02～0.06
0.08
Cylinder to Piston Clearance
0.035～0.065
0.07
Piston pin outer diameter
φ19.994～φ20
φ19.99
connecting
rod small end
the inside diameter of
φ20.015～φ20.025
φ20.04
Small end of connecting rod and piston
pin clearance
0.015～0.03
0.05