I
Crankcase Assembly
(3T
De Luxe)
Unl~ke the larger models the big ends on the 3T are not split and
it
is
necessary to
dismantle the flywheel assembly to remove the connecting rods. The lower part
of the flywheel should be held in
a
vice and the pinch bolts and nuts removed. Place
a soft metal drift through the flywheel against the opposite crank and carefully
drive out the crank by using a hammer on the drift. Drive out the other crank in
the same manner. Do not lose or damage the small tube
connecting
the two cranks.
as
this maintains the oil seal
at
this point.
If the big ends are worn
it
will be found necessary to
fit
reconditioned connecting
rods and have the crank journals reground. If the crank journals have to be re-
ground
it
is
necessary to regrind the parts of the crank journal which mate with the
fiywheel and
fit
a new flywheel with a smaller hole. Three undersizes of rods are
supplied, minus .010", minus .020" and minus ,030". All cranks which are returned
to the works for re-grinding of the journals have the timins side main bearipg journal
reground at the same time, this bearing also being available in the sa'me three
undersizes.
To Assemble the 3T Crankshaft
Thoroughly wash all parts in petrol or parahin before commencing to assemble.
Fit
the oil seal tube to the drive side crank and lightly oil the bearing portion of the
crank journal. Care should be taken to allow no oil to reach the portion which
mates with the flywheel hole. Fit the connecting rod to the drive side crank with
the marking "Flywheel Side" in
its
correct position. To align the assembly during
the fitting of the crank a round bar (+"-.003"+.000'7 should be passed through the
datum hole drilled in the lower part of the flywheel and the crank threaded over
this same bar by means of
its
own datum hole. Press the drive side crank into the
flywheel until the connecting rod
is
just free to move, then repeat the sequence for
the timing side crank. The correct side play for the rods
is
.015" to .020", and if the
clearance at one side
is
greater than this the offending crank should be pressed in
until the play is equalised. Now insert and lightly tighten the pinch bolts.
The
final alignment of the assembly should be carried out by placing a ball race over each
main bearing journal and spinning the assembly in a jig. The assembly should be
checked for truth at
3
points, the drive side mainshaft, the timing side mainshaft
and the flywheel rim; if the assembly does not run true
it
should be taken out of
the jig and the offending crank web tapped with a lead or hide hammer and then
re-checked. The maximum permissible out oftruth
is
.0005"on the end ofthe drive
side mainshaft.
Finally tighten the pinch bolt and re-check.
New crank journal diameter
=
1.3730"- 1.3735"
New T.S. bearing journal
,,
=
1.2485"- 1.2490"
New T.S. bearing
I.D.
-
--
1.2495"- 1.250W
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