Instruction manual

TAPPET ADJUSTMENT

The top ends of the two long push rods have screwed extensions. These are locked in

position by nuts, thereby providing tappet adjustment.

The correct tappet clearances, on touring models, with valves closed and engine cold,

is NIL (warm engine on competition models). This means the push rods should be free

enough to revolve and, at the same time, there should be no appreciable up and down

play.

Prepare to adjust tappets by :

Set piston to T.D.C.

Remove the three nuts, and fibre washers under them, retaining tappet cover to rocker

box.

Take away cover.

Adjust tappets on all 350 and 500 models by :

With spanners, hold the sleeve C, either valve (Illustration 13) and slacken lock nut B.

Then screw, in or out, the head A until the clearance is nil.

Tighten lock nut B and re-check the clearance.

Treat other valve in like manner.

Illustration 13

Tappet adjustment

Finally

Check adjustments so that, with no up and down movement, the long push rods are free

to revolve when the valves are closed.

Complete adjustment by :

Replace rocker tappet cover taking care to replace the fibre washer that is under each

retaining nut.

Do not over-tighten the nuts because the joint is made with a rubber fillet and undue

pressure is not necessary.

NOTE—In normal conditions tappet adjustment should not be necessary more frequently

than about every five thousand miles or after decarbonising and grinding valves.

If adjustment is found necessary more frequently the cause should be investigated

at once.

The tappet rods are made of Light Alloy, and in manufacture, the sleeve marked C in

illustration 13 is fitted to the bare rod and then the push sleeve and the rod are threaded

to take the adjusting screw marked A.

It will consequently be seen that, contrary to the practice when steel rods are used, it

is not possible to supply and fit sleeve C to an existing Light Alloy rod.

Consequently for 1951 models, the " Push Rod, bare " will only be supplied for spares

purposes complete with sleeve C already fitted and threaded.