Instruction manual

Inspect rubber fillet on rocker box side cover and renew if not perfect.

Replace the side cover ensuring that a fibre washer is fitted under each of the three

retaining nuts.

Beware of over tightening these nuts, the joint being made by the rubber fillet

excessive pressure is not necessary.

Replace the petrol tank.

DECARBONISATION

Instead of the usual stipulated mileage interval between periods of decarbonisation, it is

recommended that this is undertaken only when the need for same becomes apparent

because of excessive pinking, loss of power or generally reduced performance. When

undertaken, unless it is thought necessary to inspect the piston and rings, the cylinder

barrel is best left undisturbed. The various stages in decarbonisation are described

below.

TO REMOVE THE CYLINDER HEAD

Remove

The petrol tank.

The sparking plug.

The rocker box.

Remove the exhaust system by :

Remove nut, and washers, retaining exhaust pipe to its stay.

Remove nut, and washers, retaining silencer to its stay.

Remove complete exhaust system, by pulling away from stays and then downwards,

from the exhaust port in cylinder head.

Remove carburetter by :

Unscrew two carburetter retaining nuts.

Take away carburetter and rest on saddle.

Remove

The four bolts retaining cylinder head to barrel, and head is free to be taken away.

While doing this the push rod cover tubes will come away with the head.

If the sparking plug or cylinder head bolts resist removal, do not use force but brush

paraffin round their heads and leave for a time to soak before making further effort.

TO REMOVE AND REPLACE THE VALVES

Remove the cylinder head.

Attach the special valve spring compressing tool, Part No. 014605, to cylinder head with

the two bolts provided (Part No. 010795), see illustration 9. Then compress

the springs by screwing in evenly the two long bolts, the reduced tips of which will

engage with the countersunk depressions on the valve spring collar. The split collet can

then be withdrawn leaving the valve free. To remove the compressor slacken each of

the long bolts little by little in turn until they are clear of the valve spring top cap.

After removing the compressor tool the whole spring assembly can be lifted off. To

ensure accurate replacement it will be observed that the valve spring block to which the

prong ends of the hairpin valve springs are attached, is provided with a dowel pin which

engages a hole in the valve guide boss.