50 Tappet Adjustment - Matchless 46/G3L 1946 Maintenance Manual And Instruction Book

50 TAPPET ADJUSTMENT

The top ends of the two long push rods have screwed extensions.
in position by nuts, thereby providing tappet adjustment.
The correct tappet clearances, with valves closed and engine cold, is N I L . 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. (See Para. 48.)
Prepare to adjust tappets by :—
Remove the three nuts, and fibre washers under them, retaining tappet cover
to rocker box.
Take away cover.
Adjust tappets on all 350 and on 500 if no compression plate is fitted by:—
W i t h spanners, hold the body C, either valve (Illustration 12) 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.
Adjust tappets on 500 with compression plate fitted by:—
Turn over engine till exhaust valve is lifted.
Slacken nut on exhaust push rod. (B illustration
12.)
Turn over engine till inlet valve is fitted.
Slacken nut on inlet push rod.
12.)
Screw out, or in, the exhaust tappet adjusting
screw till tappet clearance is nill. (A illustration
12.)
Turn over engine till exhaust valve is lifted.
Tighten lock nut on exhaust push rod.
illustration 12.)
Screw out, or in, the inlet tappet adjusting
screw till tappet clearance is nill. (A illustration
12.)
Turn over engine till inlet valve is lifted.
Tighten lock nut on inlet push rod. (B illustra-
tion 12.)
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 overtighten the nuts because the joint is made with a rubber fillet and
undue pressure is not necessary.
Note:—
The part marked C in Illustration 12 is the top end of the long push rod. It is
threaded and the adjusting screw A screws into it.
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.
In no circumstances should the valve end hardened caps be omitted. These
caps are provided to prevent wear on the valve stems end and although it is
possible to lengthen the push rods sufficiently to take up the clearance resulting
from the omission of the caps, the effect of this would be to bring the edge of the
adjusting cup A at the top of its travel, dangerously close to the oil lug on the
rocker box.
(B illustration
(B
32
These are locked
Illustration 12
Tappet adjustment.