Just behind is a tapped hole for the cylinder head bolt. (Lightweight
engines only.) Close to the cylinder bore and to the right of the cylinder
head bolt hole is a smaller hole, which is the oil feed passage from the
pump to the rocker gear.
Place the gasket on the cylinder so that the oil feed hole in the cylinder
registers with the small hole in the gasket.
Put the cylinder head in position, refit the four cylinder head sleeve
nuts and the long cylinder head bolt. Do not omit the five washers. First
tighten the four sleeve nuts diagonally not one side at a time—then
tighten the long bolt, until all are firmly tightened. If a torque spanner is
available it should be set to 35 foot lbs. for the four sleeve nuts only.
Refitting the rocker box. Before attempting to refit, make sure the piston
is on T.D.C. of the firing stroke, with both cam followers down.
Use a new rocker box gasket for this assembly. In the centre portion of
this gasket is a projection with a small hole in it. There is also a similar
size hole in the cylinder head which is the oil feed passage from the oil
pump through the cylinder to the rocker gear. It will be readily seen
that if the rocker box gasket is reversed the oil feed passage will be sealed,
therefore ensure that the gasket is properly located before fitting the
rocker box. With the rocker box gasket correctly located, take up the
rocker box, pass all the holding down bolts through it, put the rocker
box into position.
Take up the two engine push rods, tilt the right side of the rocker box
upwards, then introduce the push rods through the head and cylinder.
The exhaust push rod operates with the cam follower nearest to the
contact breaker. (See Fig. 3.)
Locate the rocker arms in the push rod adjusters and first tighten the
two central rocker box bolts which have screwed extensions.
Tighten the remainder diagonally including the one inside the rocker-
box.
Washers are fitted under the heads of all these bolts.
It should be remembered that a soft gasket is used between the cylinder
head and the rocker box, therefore the degree of tightness of these bolts
is a matter of good judgment and commonsense.
Re-adjust the tappets as previously described.
IGNITION TIMING
Lightweight Models
Before setting or checking the ignition timing, make sure the contact
breaker gap at full separation, is .012".
(See details on Contact Breaker.)
Reference to Fig. 5 will indicate the principle used.
To check the timing. Position the engine as detailed for tappet adjust-
ment. Remove the sparking plug, the cover for the contact breaker and
engage top gear. Obtain a short length of stiff wire or wheel spoke about
5" long. Insert the wire through the sparking plug hole, until it touches
the piston crown. By slowly moving the rear wheel backwards and
forwards the top dead centre of the piston travel can be ascertained.
Keep the wire vertical as far as the plug hole will permit—make a mark
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