To Assemble The 3T Crankshaft - Triumph SPEED TWIN 1945 Workshop Instruction Manual

I
Crankcase Assembly (3T De Luxe)
U n l ~ k e t h e larger models the big ends on the 3T are n o t split and it is necessary t o
dismantle the flywheel assembly t o remove the connecting rods. The lower part
of t h e flywheel should be held i n
a
vice and the pinch bolts and nuts removed. Place
a soft metal d r i f t through t h e flywheel against the opposite crank and carefully
drive o u t t h e crank by using a hammer on the drift. D r i v e o u t the other crank i n
the same manner. D o n o t lose o r damage the small tube
connecting
the t w o cranks.
as
this maintains the o i l seal
a t
this point.
If the big ends are w o r n it w i l l be found necessary t o fit reconditioned connecting
rods and have the crank journals reground. If the crank journals have t o be re-
ground it i s necessary t o regrind the parts of t h e crank journal which mate w i t h the
fiywheel and fit a new flywheel w i t h a smaller hole. Three undersizes of rods are
supplied, minus .010", minus .020" and minus ,030". A l l cranks which are returned
t o t h e works for re-grinding of the journals have t h e timins side main bearipg journal
reground at the same time, this bearing also being available in the sa' m e three
undersizes.
T o A s s e m b l e t h e 3 T C r a n k s h a f t
Thoroughly wash all parts in petrol o r parahin before commencing t o assemble.
F i t the o i l seal tube t o the drive side crank and lightly oil the bearing portion of the
crank journal. Care should be taken t o allow no oil t o reach the portion which
mates w i t h the flywheel hole. Fit the connecting r o d t o t h e drive side crank w i t h
the marking "Flywheel Side" i n
i t s
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 o f i t s o w n datum hole. Press the drive side crank into the
flywheel u n t i l t h e connecting r o d i s just free t o move, then repeat the sequence for
the timing side crank. The correct side play for the rods is .015" t o .020", and if the
clearance at one side i s greater than this the offending crank should be pressed i n
until the play is equalised. N o w insert and lightly tighten the pinch bolts. The
final alignment o f the assembly should be carried out by placing a ball race over each
main bearing journal and spinning the assembly i n a jig. The assembly should be
checked for t r u t h at
3
points, the drive side mainshaft, the timing side mainshaft
and the flywheel r i m ; if t h e assembly does not run true
it
should be taken out of
the jig and t h e offending crank web tapped w i t h a lead o r hide hammer and then
re-checked. The maximum permissible o u t o f t r u t h i s .0005"on the end o f t h e drive
side mainshaft.
Finally tighten the pinch bolt and re-check.
N e w crank journal diameter
=
1.3730"- 1.3735"
N e w T.S. bearing journal
,,
=
1.2485"- 1.2490"
N e w T.S. bearing
I.D.
-
--
1.2495"- 1.250W