250 c.c. O.H.V. TWIN CYLINDER SCOOTER
ATTENTION TO VALVES
To remove a valve, compress the springs with Service Tool No. 61-5001. Take out the split collets and
remove the valve spring cup and springs, the valve will then drop down through its guide. Each
valve is removed in the same way.
The valves must be cleaned thoroughly to remove carbon deposits. Fine emery cloth can be used
sparingly but be careful not to remove. metal.
Normally it will only be necessary to grind-in the valves to their seats lightly. To do this smear a
small quantity of fine grinding paste on the face of the valve and return the valve to its seat. Grip the
valve head with Service Tool No. 61-5035 aid rotate; whilst maintaining a slight pressure. Raise the valve
and turn it to a new position every few -moments. ' Grinding should continue until both mating faces show
a uniformly matte metallic surface all round:
Camshaft and Valve Gear Arrangement. Fig. 20
If the valve seats are badly pitted
do not attempt to re-grind as this will
only wear away the valves. Instead,
the seats must be re-cut with Service
Tool No. 61-5036 and the valve re-faced
by a Dealer. If a valve guide is worn, as
shown by excessive side clearance
between stem and guide it can be
pressed out from the combustion
chamber side after the cylinder head has
been heated in boiling water for 2 or 3
minutes. It is necessary first to
remove the rocker before pressing out
an exhaust valve guide and how to do
this is explained in the next section. Press
in the new guide from the rocker side,
again with the cylinder head hot. After
fitting a new guide the valve seat
should be re-cut to ensure that it is
concentric with the guide.
Re-assembly of the valves is in
reverse order but do not forget to
remove all traces of grinding compound
and to smear the valve stems with
clean engine oil.
Dismantling and re-assembling Valve Rockers and Shafts.
In normal circumstances there will be no need to disturb the valve rocker assembly. If it is
necessary the operation is quite simple, but it must be noted that oil is pumped through passage ways
drilled in the cylinder head and then up through the posts supporting the rocker shafts and through
oilways in the shafts to lubricate valve rockers. It is, therefore, essential that the rocker shafts are re-
assembled correctly, otherwise the oil supply to the rockers will be cut off.
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