Checking/Measuring The Piston; Checking The Piston Ring End Gap - KTM 450 EXC-R EU Repair Manual

30/ENGINE - WORK ON INDIVIDUAL PARTS

Checking/measuring the piston

Checking the piston ring end gap

Check the sealing area of the cylinder head for distortion using a straight edge and
the special tool.
Feeler gauge (59029041000) (
Cylinder/cylinder head - sealing area
distortion
» If the measured value does not equal the specified value:
Change the cylinder.
400376-10
Check the piston bearing surface for damage.
» If the piston bearing surface is damaged:
Change the piston and, if necessary, the cylinder.
Check that the piston rings can move easily in the piston ring grooves.
» If the piston ring is stiff:
Clean the piston ring groove.
200160-10
Check the piston rings for damage.
» If the piston ring is damaged:
Change the piston ring.
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.
Measure the piston at the piston skirt, at right-angles to the piston pin.
Specification
Piston - diameter
Size I
Size II
Info
Piston size
200161-10
Remove the piston ring from the piston.
Place the piston ring in the cylinder and align it with the piston.
Specification
Under the upper edge of the cylinder
Measure the end gap with e feeler gauge
Specification
Piston ring end gap
Compression ring
200163-10
Oil scraper ring
» 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.
P. 179)
Tip
Use an old piston ring to clean the piston ring groove.
Info
Mount the piston ring with the marking facing upward.
94.93... 94.96 mm (3.74... 3.74 in)
94.95... 94.97 mm (3.74... 3.74 in)
is marked on the piston head.
10 mm (0.39 in)
.
P. 80)
0.1 mm ( 0.0039 in)
1 mm ( 0.04 in)
1.2 mm ( 0.05 in)
81