KTM 250 EXC, Owner'S Manual

Page: 124 / 410

5-9E
A
B
B
Checking the oil pumps for wear
– Place inner and outer rotors into the engine casing such that the
marks are adjacent to one another.
– Now, carry out the following wear measurements with a feeler
gauge
B
:
outer rotor - oil pump housing: max. 0.20 mm
outer rotor - inner rotor: max. 0.20 mm
Checking the piston
– Replace the piston in the case of excessive oil consumption or
grooves in the piston skirt.
– If reinstalling the old piston perform the following steps:
1. Piston bearing surface - check for damage.
2. Piston ring grooves - the piston rings must move easily in the groove.
Old piston rings or sandpaper (400 grit) may be used to clean the
piston ring grooves.
3. Piston rings - check for damage and end gap (see below).
Mount the oil scraper ring with the labeling "TOP" facing upwards.
Mount the rectangular ring with the labeling "O" facing upwards.
4. Piston pin: If the piston pin is heavily discolored or has score marks
it must be replaced. Also insert the piston pin into conrod and
check its bearing for play.
Piston ring end gap
– Insert piston ring into the cylinder and adjust. Piston ring must be
approx. 10 mm from top of cylinder.
– The end gap can now be checked which a feeler gauge
A
.
Compression rings: max. 0.80 mm
Oil scraper ring: max. 1.00 mm
If the end gap is larger, check piston and cylinder for wear. If piston and
cylinder wear are within the permitted tolerance limits, replace the
piston ring.