1966 Triumph TR6

1966 TRIUMPH TR6 BY THE NUMBERS
For the 1966 model year, the model lineup were TR6, TR6R, TR6SR, TR6SS, TR6C & TR6SC, all called "Trophy". Engine & Frame Numbers ran from DU24876 to DU43161, with build dates running from August 6, 1965 to July 8, 1966. The TR6C was essentially a standard 1966 Triuymph TR6 with wide-ratio gearbox, slimmer 2.3-gallon tank & Dunlop Trials Universal tires (tyres). The TR6SC was the same as the TR6C except for standard gear ratios, alloy mudguards (fenders) & a silenced exhaust. The TR6SR was basically a standard 1966 Triumph TR6 but with raised handlbars & a smaller capacity fuel tank. The prices new were around $1,200 USD.

ENGINE MODS
Shorter "Red Spot" valve springs were installed with thicker bottom cups to ensure better valve control with less spring surge. A new central flywheel, lighter by 2-1/2 pounds, was fitted to the crankshaft, while maintaining the 85% balance factor. Crankshaft end float (lateral movement) control now reverted back to the timing side main bearing (having been moved for one year only, in 1965, to the drive side). This was accomplished by a clamping washer that was interposed between the timing pinion (gear) & the main bearing inner spool. And on a drive side, a heavier, load carrying single lipped roller bearing (#RM11L) replaced the old ball bearing.

BETTER OILING
Oil was now pressure-fed to the exhaust cam followers through drillways in the crankcase, barrels & exhaust tappet block. Starting with engine #DU42399 a dowel was placed at the joint between the crankcase & barrels to stem oil seepage. The new tappet blocks were made to fit new, redesigned pushrod tubes with better sealing top & bottom.

HOT ROD
Starting with engine #DU42251, the 3/4" radius cam follwers (tappets) were replaced by the now-famous "R-type" tappets of 1-1/8" radius. The intake (inlet) valves were also increased in head diameter from 1-7/16" to 1-19/32", and the exhaust valves were enlarged to 1-7/16", just like the Triumph Bonneville T120.
GEARBOX MODS
Starting with the 1966 Triumph TR6, the speedometer drive was moved from the layshaft in the gearbox to the rear wheel. The kickstart lever was made longer for easier starting. The final drive chain oiler at the rear of the primary case was eliminated. The adjusting screw on the clutch pressure plate was fattened to 3/8" starting with #DU31820.

FRAME & RUNNING GEAR CHANGES
The 1966 Triumph TR6 featured a change in steering head angle from 65-degrees to 62-degrees to quicken steering & a fairing lug was added to the neck. A new battery-mounting system used rubber bushings running on pegs, instead of rigid mounts. The swingarm was widened by 1/4" on the right side. A new fork stem & bottom lug tightened the turning radius. The rear sprocket went back to 46 teeth. A new, wider front brake drum increased brake swept area by 40%.

BODY WORK
A new petrol (fuel) tank was slimmer & available in 3- or 4-gallon capacities. A new tank badge came with it, perhaps the most popular ever, the now-famous "eyebrow badge", so-named for its large chromed 'eyebrow' above the "Triumph" logo (see photos). With the elimination of the rear chain oiler from the primary case, the oil tank was modified to accommodate, with an adjustable metering screw in the filler cap neck that controlled the amount of oil that was allowed to run down to the chain. Along with these mods, the top end oil line was now being fed off the top of the return pipe, rather than below the tank, as before. This led to weak & often erratic top end oiling which in turn caused premature rocker arm wear. A service kit was soon issued to reverse this.

NEW 12-VOLT ELECTRICS
Every 1966 Triumph TR6 (except the TR6C) got a 12-volt Zener Diode mounted to the battery box, as the whole system switched to 12 volts. Triumph Motorcycles opted for two Lucan SKZ9E 6-volt batteries hooked up in series to produce 12 volts. However, by #DU32985 they switched to a single Lucas PUZ5A 12-volt battery, with modified carrier to match. The 7-inch chromed headlight contained the ignition warning & high beam indicator lights (after #DU29247). The 12-volt Lucas MA12 coils were still located as before, although some US models got the smaller Siba 3200/1 coils. A Lucas 88SA light switch remained on the left-side cover as did a new ignition switch. The location of the Zener Diode had to be changed slightly due to overheating problems, starting with #DU40436.

1966 Triumph TR6 SPECIFICATIONS

Model Designations:

TR6S/S

TR6C

TR6SC

TR6R

TR6SR

Engine Type

Displacement

Bore & Stroke

Compression

Carburetor

Ignition

Engine output

Primary drive

Primary sprockets

Clutch

Gearbox

Ratios, overall:

1st, bottom

2nd

3rd

4th, top

Final drive

Final sprockets

Frame type

Suspension, front

Suspension, rear

Brake, front

Brake, rear

Tire, front

Tire, rear

Fuel Capacity

Wheelbase

Seat height

Ground clearance

Dry Weight


Street scrambler

Off-road/street (dual purpose/enduro)

Off-road, competition

Roadster

High-performance roadster

Air-cooled OHV vertical twin

649cc / 40.0 ci

71mm X 82mm / 2.79" X 3.23"

8.5:1

1- Amal Monobloc, 1-1/8"

Battery & coil, Lucas

42 bhp @ 6500 rpm

3/8" triplex chain X 84 links

Engine 29T X Clutch 58T

Multi-plate, wet

4-speed constant-mesh, right-foot shift


11.8:1

8.17:1

6.76:1

5.84:1

5/8" X .400" X 3/8" chain X 106 links

Gearbox 19T X Rear 47T

Brazed lug, full-cradle, single downtube

Telescopic fork, hydraulic damping

Swing arm, 2 Girling dampers

8" SLS drum, full-width

7" SLS drum, one-side

3.25" X 19" Dunlop

4.00" X 18" Dunlop

2.5 Imp gal (US)/4 Imp gal (UK & export)

54.5" / 140.3 cm

32.5" / 77.5 cm

5.0" / 12.7 cm

363 lbs / 165 kg

MORE TRIUMPH TR6 PAGES:
Triumph TR6
Triumph TR6, Pre-Unit (1956-1962)
.....1956
.....1957
.....1958
.....1959
.....1960
.....1961
.....1962
Triumph TR6, Unit-Construction (1963-1970)
.....1963
.....1964
.....1965
.....1966
.....1967
.....1968
.....1969
.....1970
Triumph TR6, Oil-in-Frame (1971-1972)
.....1971
.....1972
Triumph TR7
.....1973
.....1976

OTHER TRIUMPHS:
Triumph Bonneville
Triumph Trophy
Triumph Tiger
Triumph Thunderbird
Triumph Trident
Triumph X-75 Hurricane


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COMPLETE BOOK OF CLASSIC & MODERN TRIUMPHS


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TRIUMPH MOTORCYCLE RESTORATION, PRE-UNIT


TRIUMPH BONNEVILLE & TR6 RESTORATION GUIDE: 1956-1983


TALES OF TRIUMPH MOTORCYCLES & THE MERIDEN FACTORY


TRIUMPH 650 & 750 TWINS OWNERS WORKSHOP MANUAL, 1963-1983


TRIUMPH BONNEVILLE: ESSENTIAL BUYER’S GUIDE


TRIUMPH BONNEVILLE: PORTRAIT OF A LEGEND


ILLUSTRATED TRIUMPH BUYER’S GUIDE, by Roy Bacon


TRIUMPH BONNEVILLE, 2001-2015


TRIUMPH: PRODUCTION TESTERS TALES FROM MERIDEN


TRIUMPH MOTORCYCLE RESTORATION GUIDE


TRIUMPH OWNERS HANDBOOK, UNIT-CONSTRUCTION 350 & 500, Kindle


TRIUMPH ILLUSTRATED WORKSHOP MANUAL 1945-1955, by Clymer


TRIUMPH TWINS & TRIPLES


FACTORY-ORIGINAL TRIUMPH TWINS, 1938-1962


TRIUMPH BONNEVILLE & TR6, by Timothy Remus


TRIUMPH MOTORCYCLES: FROM SPEED TWIN TO BONNEVILLE


TRIUMPH MOTORCYCLES: THEIR RENAISSANCE & THE HINKLEY FACTORY


TRIUMPH PRE-UNIT TWINS OWNERS WORKSHOP MANUAL


TRIUMPH THRUXTON BONNEVILLE 1959-1969


TRIUMPH MOTORCYCLES ILLUSTRATED WORKSHOP MANUAL 1937-1951, by Clymer


TURNER’S TRIUMPHS: EDWARD TURNER & HIS TRIUMPHS


TRIUMPH TWIN RESTORATION, by Roy Bacon


TRIUMPH TIGER CUB & TERRIER 1952-1968, Haynes Repair Manual


TRIUMPH 675 DAYTONA & SPEED TRIPLE REPAIR MANUAL 2006-2010, Haynes


CLASSIC MOTORCYCLES: TRIUMPH


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BONNIE: THE DEVELOPMENT OF THE TRIUMPH BONNEVILLE


TRIUMPH SINGLES: EARLY DAYS TO 1974, by Roy Bacon


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THE TRIUMPH STORY: RACING & PRODUCTION MODELS 1902-PRESENT


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HINKLEY TRIUMPHS: THE FIRST GENERATION


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