Ash White; Dull Black; Light Brown - Triumph SPEED TWIN 1945 Workshop Instruction Manual

following conditions:
ASH
WHITE.
This i s a sign that t h e plug is over-heating.
Usual cause is the m i x t u r e
strength t o o weak (a common cause being a faulty carburetter t o cylinder head joint
o r t h e ignition t o o far retarded.
DULL BLACK. This indicates that t h e plug is running t o o cold or, i n other words
the insulator i s insufficiently h o t t o burn off the carbon. This i s caused by t o o rich
a mixture o r the engine left r ~ n n i n g w i t h
a
generous slow running setting (quality
LIGHT B R O W N .
This shows that the m i x t u r e strength is correct and the engine
is
running at the right temperature.
Before re-fitting the plugs, make sure that the copper washers i r e n o t defective i n
any way. I f they have become w o r n and flattened, fit new ones t o ensure that a
gastight joint is obtained.
& !
1
When installing plugs, f i r s t screw the plugs down by hand as far as possible, then use
i
k'
$
spanner f o r tightening only.
Always use a tubular box spanner t o avoid possib!e
$
fracture t o the insulator, b u t do n o t under any circumstances use a movable wrench.
i
; $
Paint splashes, accumulation of grime and dust etc.. on the top halfof the insulator are
1
gj
often responsible for poor plug performance.
Plugs should be wiped frequently
, g
. '
with a clean rag.
i
1
To save p e t r o l and prevent difficult starring, plugs should be cleaned and tested at
regulai intervals, and it i s suggested that this service be performed at your garage o n
I
a special " A i r Blast" service unit.
Plugs which are allowed t o remain oily and d i r t y
1 w i t h corroded electrodes w i l l seriously impair the efficient running of the m o t o r
1
and waste precious petrol.
To obtain maximum efficiency from the engine and also t o maintain good petrol
consumption which the motorcycle has when new, plugs should be changed at
,
!
regular intervals
as
old plugs are wasteful and cauze poor and sluggish running. W e
recommend inspection, cleaning and testing every
3,000
miles
(5,000
kmr.), and
it
W i l l
be found economical
td
replace w i t h new ones annually.