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TO REMOVE T W I N SEAT
Remove two bolts under the rear end of the seat, release the nuts securing the front
portion of the seat, which now can be lifted off.
TO REMOVE THE PETROL TANK
Close both petrol taps, unscrew the two cap nuts securing the petrol pipe (watch for 4
fibre washers each side of the banjo unions). Take out two bolts securing the frornt of
the petrol tank and a further bolt securing the rear, noting the location of the tank bolt
rubbers and spacers, the front ones are thick the rear are thin, the steel washers are
also dissimilar.
TO REMOVE THE ROCKER B O X
Remove the three nuts and fibre washers securing the rocker box cover, also the sparking
plug.
Turn the engine until both valves are closed, i.e., after the inlet valve has opened and just
closed.
Remove two ruts and the bolt securing the engine steady bracket to the rocker box and
frame.
Disconnect valve lifter cable.
Take out the nine bolts securing the rocker box to the cylinder head (one of these bolts
is inside the rocker box (see illustration 2), the location of these bolts must be noted
as they are dissimilar.
Tilt upwards the right side of the rocker box, extract both push rods and identify their
location for replacement in their original positions, remove the rocker box from the
cylinder head.
TO REMOVE THE CYLINDER HEAD
Remove the exhaust pipe and silencer as one unit, then the accessory compartment cover
and air filter tube if fitted.
from the exhaust port which can cause the end of the pipe to close in and result in gas
leakage, also movement between the pipe and the port when the engine is hot. Instead
squirt a little paraffin or petrol into the port and try again.
Unscrew the cap on the carburetter mixing chamber, cake out both slides, wrap them
in a piece of rag and attach it to the frame, out of harm's way.
Unscrew the petrol pipe union and take away the petrol pipe. Four sleeve nuts and one
bolt retains the cylinder head to the barrel, with these removed, the cylinder head with
carburetter attached to it can be separated from the cylinder.
DECARBONISATION
Instead of the usual stipulated mileage interval between periods of decarbonisation, it is
recommended that this is undertaken only when the need becomes apparent because of
loss in power, heavy petrol consumption or generally reduced performance.
When undertaken, unless it is thought necessary to inspect the piston and rings, the
cylinder barrel is best left undisturbed.
Before starting this work have available a gasket set, and if the machine has covered
considerable mileage, a new set of piston rings also,
Carbon formed on the piston crown and in the sphere of the cylinder head, can be
scraped off with a cheap steel rule, with the sharp corners removed, or similar tool.
Deal with the cylinder head before removing the valves, and do not use emery cloth or
other abrasives for this work,
TO REMOVE A N D REPLACE THE VALVES A N D GUIDES
The valve springs are removed by inserting the index finger through the coil of the
spring and pulling upwards sharply.
A light tap on the valve spring collar will expose the valve split collets (which should be
put in a place of safety), then take out the valve.
Both valve guides are located by an external circlip, the cylinder head must be gently and
uniformly heated before attempting to remove or replace the guides.
With the head pre-heated tap the guide upwards out of the port sufficiently to enable the
circlip to be prised out of its groove.
the cylinder head.
When refitting the guides, pre-heat the head and verify that the oil
holes are in alignment with holes in the cylinder head.
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Do not rock the exhaust pipe sideways unduly to extract it
Reheat the head and drive out the guides through
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