TOP Perfomance PIAGGIO 50 4T Manual Del Usuario página 12

– Remove the camshaft gear bolt by holding the rotor nut.
– Remove the chain tightener and the gear of the camshaft. In
order to avoid the timing chain falling in the crankcase, fi x it
with an iron wire.
– Remove two M6 screws that fi x the head to the crankcase.
– Loosen the four M6 head nuts.
– Unscrew the four previously loosened M6 nuts.
– Remove head, chain guide sliding block and cylinder from
crankcase.
– Use a clean rag to protect the crankcase against dirt and
foreign material.
– Remove the piston circlip, pull out the gudgeon pin and take off
the piston from the con-rod.
ASSEMBLY
Carefully clean the cylinder mating surface on the crankcase from
any residue of the original sealing paste. Clean and degrease the
TOP cylinder and check that the cylinder base enters smoothly in
the casings hole by inserting it fully home. If there are hard spots, it
is recommended to remove them by ensuring that no shaving enters
in the crankcase.
•
Head preparation
– Remove the carbon deposits and the gasket residuals from the
head surface and from the combustion chamber.
– Carry out a valve seal test by pouring clean solvent in the inlet
and exhaust ducts, and check if there is any leak.
If there is a fl uid leak between valves and valve seats you have
to remove the valves and check the clearance between stems
and guides or ensure that the valves are not bent or worn.
Replace the unsuitable parts and remove the carbon deposits,
then proceed lapping the valves with the special abrasive
paste. Carefully clean the head and all parts, reassemble them
and carry out again the valve seal test.
Should it be necessary, the head lapping must be done by a qualifi ed
workshop. Otherwise place a damp sheet of glass paper (1000 grain)
on a surface plate and lap the head by moving it like an eight.
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