Triumph TR2 Service Instructions Manual page 77

ENGINE
23. ENGINE NOISES
(a) Main Bearing Knock
This knock
can
usually be identified
by its dully heavy metallic note which
increases with frequency as the engine
speed and load rises. A main bearing
knock is particularly noticeable when
the engine is running very slowly and
consequently unevenly, it is more
pronounced with advanced ignition.
When this bearing knock is experienced
it can be explained by one of the
following faults and should be treated
accordingly.
(i) Unsuitable grade of oil or badly
diluted oil supply.
(ii) Low oil pressure.
(iii) InsufFident oil in sump.
(iv) Excessive bearing clearance
caused by worn journal and/or
bearings.
(b) Crankshaft End Float
When a knock is being caused by the
development of end float, it will be
found most noticeable when the engine
is running at idling speeds. This
knock can temporarily be eliminated
by operating the clutch.
(c) Big End Bearing Knock
A big end bearing knock is lighter in
note than that experienced with a
main bearing. It will be evident at
idling speeds and will increase with
engine speed.
The best test for this noise is to detach
the lead from each sparking plu
in
turn and reconnecting the lead
W
h
st
flicking the throttle open. On re-
connection of the lead, a light thud will
be audible where the beanng looseness
or correcting misalignment exists, fur-
ther investigation can be carried out
to that particular rod or rods.
In addition to the knock being caused
by excessive bearing clearance it is
sometimes caused by :-
(i) Unsuitable grade of oil or badly
diluted supply.
(ii) Insufficient supply of oil.
(iii) Low oil pressure.
(d)
Small End Knocks
As the gudgeon pin used in this model
is able to float in the piston and the
bearing in the connecting rod, a knock
may arise owing to slackness in the
small end bush or the piston bosses.
The knock will make itself audible
under idling conditions or at road
speeds between 20--30 m.p.h. (32-
48 km.p.h.).
To test for a gudgeon pin knock, cut
out each cylinder one at a time by
disconnecting the plug leads. The
offending gudgeon pin will be identi-
fied by the fact that a double knock is
caused when the disconnection of the
plug lead is made.
With complaints of this nature, the
following possible causes should be
examined.
(i) A too tight gudgeon pin.
(ii) A gudgeon pin slack in the con-
necting rod bush or piston boss
(see page 2 for gudgeon pin
clearance).
(iii) Misalignment of connecting rod
allowing connecting. rod bush to
foul the piston bosses.
(e) Piston Knock (Piston Slap)
This will increase with the application
of load up to 30 m.p.h. (48 km.p.h.)
but only in very bad cases will it con-
tinue to be audible over that speed. In
some cases piston knock will only be
evident when the engine is started from
cold and wi. 1 disappear as the engine
warms. In such cases it is suggested
that the engine is left untouched.
A suggested method of locating the
offending piston is to engage a gear and
with the hand brake hard on, just let
the clutch in sufficiently to apply a load
with the engine at a moderate speed.
By detaching a spark plug lead and
thus putting a cylinder out of action, it
is possible to cut out the knock and so
determine the offending piston.
Faults in the engine components listed
hereafter often contribute to piston