Yingang YG125-25, Maintenance Manual

Page: 60 / 144

YG125-25 Maintenance Manual Cylinder Head, Cylinder and Piston
Check the cylinder wall for deformation, and use the edge
ruler and clearance gauge to inspect the planeness of the
cylinder’s joining surface.
Maintenance limit:
≤
0.05mm.
Measure the cylinder internal diameter. The measurement
shall be made at three positions: top, middle and bottom,
measure in two crossing directions for each position, and
finally calculate their mean value.
Maintenance limit:
≤φ
85.10mm
Work out the Cylinder’s grade slope.
Maintenance limit:
≤
0.05mm
Work out the Cylinder’s roundness.
Maintenance limit:
≤
0.05mm
Piston
To remove the piston:
1. Remove the cylinder head cover (See Removal of
cylinder head cover)
2. Remove the camshaft (See Removal of camshaft).
3. Remove the cylinder head (See Removal of cylinder
head).
4. Remove the cylinder (See Removal of cylinder)
5. Remove the piston pin retainer at one side, and pull
out the piston pin.
6. Take out the piston.
Notice:
Do not drop the piston pin retainer into the crankcase.
To mount the piston pin:
1. Coat engine oil on the piston pin surface and let the
oil go through the piston and the small end bore of
the crankshaft link rod.
2. Mount the new piston pin retainer, with the gap
staggering the piston gap by more than 15
°
as
shown in the above.
3. Mount the cylinder (See Installation of cylinder).
4. Mount the cylinder head (See Installation of cylinder
head);
5. Mount the camshaft (See Installation of camshaft).
6. Mount the cylinder head cover (See Installation of
cylinder head cover).
Notice:
Assemble the piston with the top side with the marker
“ ” facing exhaust side.
Clearance gauge
Edge ruler
Clearance gauge
Piston
Piston pin
Piston pin retainer
Piston notc
h
Piston pin retainer gap
61