Fantic Motor TL 250, Workshop Manual

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CHAPTER 18
ENGINE
WORKSHOP MANUAL
TL 250
18.4.7 Inspect the camshaft parts
Check the surface of the camshaft for wear or damage, and
make sure that the bearings on both sides of the camshaft are
not rotating slower than they should.
If you find significant wear or see the bearings are having
trouble rotating, you will need to install new camshaft parts.
Check the decompressor exhaust valve gear assembly for
cracks or breakage, and make sure that the exhaust valve
centrifugal system and shaft have not come loose.
In either of these cases, you will need to install a new exhaust
valve assembly.
18.4.8 Inspect the cylinder head
Check whether the cylinder head has a poor airtight seal. If this
is the case, you will need to install a new cylinder head or valve.
Check the spark plug hole and valve seat for cracks.
Check the cylinder for warp, and measure the flatness of the
cylinder head using a straight edge and a feeler gauge.
18.4.9 Inspect and lap the valve seat
Clean the combustion chamber to remove carbon deposits.
Coat the valve seat "A" with a thin, even layer of red ink and
carefully insert the valve in the seat, tapping on the valve and
holding it still. Then spin it round and check whether there
are any breaks in the marking it leaves on the valve's contact
surface. If this is the case, lap the valve seat.
First, clean the intake and exhaust valve seats to remove
carbon deposits, then apply abrasive material to the valve seat
and attach the rubber suction cup on the end of the lapping
tool to the valve.
18.4.10 Inspect the valve guide
Measure the inside diameter "A" of each valve guide using a
dial-gauge and perform the required checks.
Service limit value: Ø 5,035 mm
Remove carbon deposits that have built up on the valve guide
before measuring the guide's diameter.