30/ENGINE - WORK ON INDIVIDUAL PARTS
114
–
Clean the piston ring groove.
Tip
Use an old piston ring to clean the piston ring groove.
–
Check the piston rings for damage.
» If the piston ring is damaged:
–
Change the piston ring.
Info
Mount the piston ring with the marking facing upward.
–
Check the piston pin for discoloration or signs of wear.
» If the piston pin has strong discoloration/signs of wear:
–
Change the piston pin.
–
Insert the piston pin into the connecting rod and check the bearing for play.
» If the piston pin bearing has too much play:
–
Change the connecting rod and the piston pin.
301758-10
–
Measure the piston at the piston skirt, at right angles to the piston pin, at a dis-
tance
.
Guideline
Distance
31.5 mm (1.24 in)
Piston - diameter
Size I
101.955… 101.965 mm (4.01397…
4.01436 in)
Size II
101.965… 101.975 mm (4.01436…
4.01476 in)
Info
Piston size
is marked on the piston head.
18.14
Checking piston ring end gap
300098-10
–
Remove the piston ring from the piston.
–
Place the piston ring in the cylinder and align it with the piston.
Guideline
Under the upper edge of the cylinder
10 mm (0.39 in)
–
Measure the end gap with a feeler gauge
.
Guideline
Piston ring end gap
Compression rings
≤
0.80 mm (
≤
0.0315 in)
Oil scraper ring
≤
1.00 mm (
≤
0.0394 in)
» If the end gap is more than the specified value:
–
Check/measure the cylinder. (
» If the cylinder wear is within the tolerance range:
–
Change the piston ring.
–
Mount the piston ring with the marking facing toward the piston head.
Summary of Contents for 690 SMC 2008
Page 1: ...REPAIR MANUAL 2008 690 SMC EU 690 SMC AUS UK 690 SMC USA Article no 3206042en...
Page 2: ......
Page 185: ...183...
