A cast iron cylinder head had valves enclosed by cast alloy
rocker boxes with an overhead oil feed taken off the scavenge
side of the lubrication system, as oil was returned from the dry-
sump crankcase to the external oil tank. The inlet cam drove a
plunger-type oil pump. Ignition was by magneto, located just
behind the cylinders, while electrical current was produced by a
dynamo mounted in front of the engine.
A right-side foot shift lever
stirred the gears in the sepa-
rate 4-speed transmission and
a 5-plate clutch lived under a
highly polished primary cover
on the left side of the engine.
Power was transmitted from
the engine to the transmission
by chain through a ramp-and-
spring cush drive sprocket to
the clutch. All of these com-
ponents were placed in a rigid-
style frame with a hydraulic fork
up front.
Triumph’s Thunderbird
proved to be a successful
motorcycle, and in 1954 the
company took the concept a
step further and introduced the
T110 with a revised cast-iron
cylinder head, higher-compres-
sion pistons with a ratio of 8.5:1
and a larger Amal carburetor.
Also new was the swingarm
frame and at that time, the T110
was Triumph’s fastest 650cc
production motorcycle.
The Trophy models
The TR5 Trophy debuted in 1949. Based on the Speed Twin
and its 500cc engine, the Trophy had a high-level exhaust and the
all-alloy, square-barrel top end from Triumph’s WWII generator
engine, and in 1951 the model was equipped with revised close-
fin alloy cylinders and head.
Then, in 1956, Triumph offered the 650cc TR6 Trophy, an
offroader equipped with the
larger single-carb 649cc engine
of the T110 Tiger but updated
with an aluminum head and
8:1 pistons. The Trophy was in
essence a street scrambler that
could be ridden to work during
the week and then, come the
weekend, on the dirt thanks
to a quickly detachable Lucas
headlight, high-level exhaust
and moisture-proof magneto.
The TR6, like the 6T before
it, sold well in the U.S., and
the model was spun into three
derivatives: the TR6A, with
freer-flowing low-level exhaust
pipes and a tachometer; the
TR6B, with a mid-level 2-into-1
exhaust setup and no tachom-
eter; and the TR6C with the
exhaust system of the T110 and
no tachometer. By 1958, the
TR6’s alloy cylinder head was
slightly altered and, according
to author Ian Falloon in his book
The Complete Book of Classic andhttp://www.MotorcycleClassics.com 21
The air-cooled 649cc twin puts out about 40 horsepower,
plenty for a bike weighing just 365 pounds dry.