Mounting the chain tensioner
– Press the chain tensioner together up to the first notch and lock in
this position. Slide into the hole in the cylinder heads together with
a new O-ring.
NOTE:
– Check and lock the chain tensioner: see Chapter 5.
– The piston
1 must protrude approx. 3 mm out of the chain
tensioner.
– Mount the plug with a new seal ring and tighten to 25 Nm.
– Press against the piston of the chain tensioner with a screwdriver to
cause the mounting lock to yield and the piston to extend. The
chain tensioner rail will be loaded and the timing chain tensioned.
NOTE: if you press against the chain tensioner now it will lock. This
makes sure that the timing chain is tensioned when you start the
engine and not enough oil pressure has been built up yet.
!
CAUTION
!
I
F THE CHAIN TENSIONER IS NOT LOCKED AND RELIEVED AFTER ASSEMBLY AS
DESCRIBED IN
CHAPTER 5, THE TIMING CHAIN WILL SKIP WHEN THE ENGINE IS
STARTED
, RESULTING IN ENGINE DAMAGE.
Checking the valve clearance
– Use the feeler gauge 590.29.041.000 to measure the valve
clearance:
Intake valves 0.10 - 0.20 mm
Exhaust valves 0.12 - 0.22 mm
– Write down any deviations from the specified valve clearance,
remove the camshafts and measure the thickness of the installed
shims. If the measured valve clearance is too small, use thinner
shims; if the valve clearance is too large, install thicker shims.
Shims are available in thicknesses of 1.72 to 2.60 mm in
graduations of 0.04 mm.
– Check the valve clearance again after assembly and correct again if
necessary.
– Unscrew the engine locking screw, remount with the CU-seal ring
and tighten to 20 Nm.
6-14
Repair manual KTM 250 -F Art.-No. 3.206.052-E
1
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