9/26/2017
Service Manual Model J
http://www.sky-net.org.uk/kelvin/diesel/j_range/man/index.html
10/17
from the end of the magneto. If the device is not working, remove the inspection door
and examine the springs.
58. SPARKING PLUG, CARE OF.--Porcelain plugs must be handled with care. A
spanner carelessly applied may produce in the porcelain an invisible crack which in
time holds moisture and causes the plug to short. The thread of the sparking plug
should be oiled.
59. SPARKING PLUG TEST.--Take out plug, lay it on engine so that its body alone
makes contact, turn engine by hand. If no spark results
60. SPARKING PLUG ADJUSTMENT.--The spark gap becomes wider with use,
and the points should be bent to maintain the gap between .016" and .020". The size
of the spark is in proportion to the width of the gap. A spark too small may fail to start
the engine, but a gap too wide may fail to produce a spark.
*61. SPARKING PLUGS DAMP.--The combustion of air and petrol produces water
vapour, some of which condenses on the sparking plugs. The sparking plugs supplied
by us are so arranged that this water can be blown off before starting by turning the
engine by hand with the sparking plug handles slackened one half turn. Note that this
cannot be done with ordinary sparking plugs.
62. SPARKING PLUG ON CRANKCASE.--Certain engines are fitted with
magnetos which produce more sparks than are required. The superfluous sparks are
led by cable to a sparking plug carried in a holder on top of the crankcase. This plug
and its connections must be kept in working order or the magneto may be damaged.
63. CYLINDER LINER.--When the internal diameter, about 3/4" from the top,
exceeds 4.265" the liner should be renewed. If you have no micrometer, make a length
bar of iron wire about 3/16" and a fit for the liner at the top. With this and a set of
"feelers" it is possible to measure the diameter where the wear occurs. The liners are
pressed into the cylinder and may be withdrawn upwards, without removing the
cylinders, by means of a tool loaned on request
.
*64. AIR COCK.--On the air chamber of the water pump will be found an air cock.
This should be opened for a moment occasionally to fill the air chamber and so
prevent water hammer. It is necessary to close the sea cock while doing so.
65. WATER REGULATOR.--This is automatic in action. Withdraw the valve
occasionally to see that it is free. Control is by a restricting plate fixed between the
regulator and the flange of the small pipe. The size stamped on the regulator indicates
the original size of the hole in the restricting plate. Restriction bushes within the
water- connections distribute the water equally.
*66. WATER PUMP STRAINER.--This should be cleared regularly. To run until it
chokes is dangerous. The strainer requires little attention at sea, but frequent attention
if the engine is run with the boat at rest in shallow water, especially if the reverse gear
has been in action as that stirs up the water.
