1971 TRIUMPH TR6


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The 1971 Triumph TR6 saw the introduction of the new oil-bearing frame & all new cycle gear. This photo is of a '71 TR6 Tiger. The TR6 had a single carburetor while the Bonneville had two.

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1971 TRIUMPH TR6 BY THE NUMBERS
All TR6's were known as "Triumph Tiger". There were 4 basic models: TR6R (Roadster & now the standard version), TR6C (with high pipes), TR6P (Police), & TR6RV (a Roadster with an optional 5-speed transmission). Engine & Frame Numbers ran from PE003157 to HE029817, built from November 11, 1970 to August 7, 1971.

BIG CHANGES
The 1971 Triumph TR6 & it's sister bike, the 1971 T120 Bonneville were complete revamped from stem to stern, with a complete redesign that included a new oil-bearing frame, new forks, new wheels with conical hubs, new cycle gear & bodywork & a whole new look. The engines were about the only components that didn't get substantial change (other than the option of a 5-speed gearbox for the first time). On the surface, this sounds like a really good thing to do for Triumph Motorcycles, especially considering the withering competition beginning to pour in from Japan. Unfortunately, quite the opposite proved to be the case.

1971 triumph tr6 engine, 71 triumph 650, 71 triumph bonneville, triumph motorcycle pictures

TROUBLE IN PARADISE
After years of market & racetrack success, Triumph was on a roll, at the end of the 1960s. But times were a'changin', as they say. DOHC 450 Hondas & of course the mighty Honda 750 Four changed the game. Triumph twins were no longer the weapon of choice for high-performance riders. They were beginning to show their obsolescence. The Japanese motorcycle makers, Honda in particular, were advancing the art & science of motorcycles, motorcycle design & manufacture, looking for new & better ways to do things. The British motorcycle industry, at the time, were trying to find ways to reuse their old, antiquated designs & tooling, they didn't want to invest in new designs or manufacturing techniques. Some of the tooling used to build the 1971 Triumph TR6 were more than 3 decades old, by this time! Some machines were worn so badly that blocks of wood had to be used to take up the play!!

BEHIND THE SCENES SHENANIGANS
Unknown to most people at the time, Triumph Motorcycleswas solely owned by BSA. You see, back in the 1930s, Triumph was in financial trouble & so was bought for a song by Ariel Motorcycles owner, Jack Sangster. He is the one who brought in Edward Turner to design the seminal 1938 Triumph Speed Twin, the bike that set the pattern for every British vertical twin for the next 45 years. Sangster was more of a wheeler-dealer than a motorcycle enthusiast. He just saw the business as a way to make money. Pursuant to this, he sold Triumph to BSA in 1951 & retained a seat on the BSA Board of Directors. At the time, BSA was one of the largest multinational corporations in the world, making everything from armaments & steel to buses & heavy equipment & they were flush with success. By the early 1960s however, Sangster had presided over the selling off, at bargain prices, most of the company's assets, until by the mid-60s, what was left of BSA was weak & out of money. Triumph's success was just about the only bright spot for BSA, yet BSA hated Triumph as a rival. Management was horrible, bad decisions to even worse & they rode their once-successful empire into the ground!

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THE UMBERSLADE HALL DEBACLE
After years of underinvestment & bad management, BSA got a big ideas: Rather than spend our dwindling resources on new motorcycles, lets build a lavish 'technology center' at this cool old mansion in the country (called Umberslade Hall), then bring in lots of high-priced talent that has no motorcycle experience. Aerospace engineers redesigned the entire Triumph 650 line with new oil-bearing frames, forks, wheels, the works. But delays in getting the Meriden factory the final blueprints pushed the production start date all the way out to November 1970 (it would normally have been in August). When the factory built the first frame & tried to put an engine in it, they found that it would not fit. Once in place, it fit fine, it just couldn't be shoe-horned in, on the assemblyline.

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1971 Triumph TR6C TROPHY

TR6"C" FOR "COMPETITION"
In days of old, the "C" on the end of a Triumph's model-name nomenclature always denoted the "Competition" model, or accurately the "Off-Road Model". Back in the 60s and 70s, they called bikes like this "Scramblers", generally characterized by their high exhaust pipes, snaking along the left side of the bike. Originally conceived to give more ground clearance in TT and "Scrambles" races, where they were always turning left, they moved the exhaust out from the bottom of the engine on either side, and pushed them up as high as practically possible. Many a leg have been burned on such pipes, even despite the heavy heat-shielding. Back in the day, there were real differences between the TR6Cs and the street-going TR6Rs. But by 1971, those differences had largely vanished, mostly in an effort to cut costs. Now the only real difference was the exhaust pipes and the name badges.

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HASTY CHANGES
The engineers at the Meriden had to quickly create a solution, as the design of the frame was fixed & couldn't be changed. They hastily designed a new cylinder head, rocker boxes & 2-piece head bolts, all as a means of creating the needed clearance to install the engine.

OTHER ENGINE CHANGES
The new rocker boxes now had screwed-in access plugs in either side, which allowed better access for a feeler gauge during valve adjustment. New pushrod tubes now featured an unbroken top rib with holes drilled through it, rather than the former castellated design, aimed at curing oil leaks. Staring with #GE27029, a new metric timing-side mainbearing was installed, requiring a new crankcase half & modified crankshaft dimensions.

GEARBOX: FINALLY, A 5-SPEED!
Starting with #GE027729, a long-awaited 5-speed gearbox became optional on all 650 twin models, including the 1971 Triumph TR6, which with 5-speed was known as a TR6V. The same old 4-speed gearbox was still standard equipment across the model line.

NEW OIL-BEARING FRAME
Despite all the teething problems, the new Umberslade Hall oil-bearing frame for the 1971 Triumph TR6 & the 1971 Triumph Bonneville was actually a pretty good frame. For the first time in Triumph Motorcycle history, it was an all-welded, one-piece frame. The new twin-downtube frame had a large 2-1/2" diameter backbone & seat post that ran from the steering head to the bottom of the frame & it was filled with oil. It was all supposed to be filled with oil, about 6 pints, more capacity than the old oil tank it replaced. However, the "brain trust" at Umberslade Hall decided, at the last minute, to place the oil filler under the nose of the seat, instead of just aft of the steering head. One possible reason was said to be 'oil frothing'. Either way, it cut oil capacity to just 4 pints, now 1 pint short of the old oil tank. It had a much stronger swingarm pivot, with a new forked swingarm. The steering head now had tapered roller bearings.

SUSPENSION & CYCLE GEAR
Rear suspension units (shock absorbers) were 12.9" Girlings with exposed chromed 110lb springs. The forks were all new & very modern & attractive. It had hard-chromed stanchions & alloy sliders with 4 studs at the bottom of each one, retaining each end of the axle. Gone were the gaiters, now it had neat little rubber sliders. Looked great, but the exposed fork legs allowed dirt in & wore the seals prematurely. The sliders had no bushings, so the rode directly on the stanchions & this too wore prematurely, a condition that could only be cured with all new sliders.

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COOL NEW CONICAL HUBS
One of the really cool features of the new-for- 1971 Triumph TR6, T120 Bonneville, and T150 Trident was a new set of alloy conical brake hubs, front & rear. While they are some of the best-looking brakes ever made (I guess that depends on personal taste), they really didn't work all that well. The 8-inch TLS (Twin Leading Shoe) front brake was weak from the start & cripped by poor leverage in the actuator arms & cams. The 7-inch rear SLS (Single Leading Shoe) brake wasn't much better & needed tweaking to get it to work well. Although neither worked as well as the units they replaced. One has to wonder why the Whiz Kids at Umberslade Hall spent their meager resources developing two completely new drum brakes, when just 2 models years later, the front drum was due to be replaced with a single disk brake. And remember, this was 1971. Honda had had front disk brakes since 1969, not to mention 5-speeds & electric starters. Wouldn't the money have been better spent on some of those things? Oh well, that was the thinking of the day, within the British Motorcycle industry as a whole. And it cost them the game.

BODYWORK & MISCELLANEOUS
A new rubber-mounted 3-gallon fuel tank was now mounted via one central hold-down bolt. The previous year's tank badge & rubber kneepads were retained. A 4-gallon tank was available as an option on US models & was standard in the UK. New chromed front & rear mudguards (fenders) were fitted with thick wire stays that were rubber mounted at the forks. UK models got a black plastic front fender number plate (license plate bracket). New exhaust pipes featured an "H" crossover pipe & modern-looking megaphones, with the exception of the TR6C which had high pipes running along the left side. The air filters were now integrated into the square, flat, plastic sidecovers which enclosed the battery & electrics. A new flat 'pancake' headlight was mounted on thin chromed-wire brackets, also rubber-mounted. The headlight housing held 3 warning lights (ignition/oil warning; high beam; turn signals) & a 2-position (pilot & headlight) rotary headlight switch. There were turn signals standard & all new Lucas handlebar controls (which were terrible in every way). A new Lucas rotary combined ignition & headlight switch rested in the right side cover. The new Smiths 150mph speedo (SSM5007/00A) & RSM 3003/14 tachometer (rev counter) were housed in rubber cups attached to the top fork nuts.

SOME MISFIRES
So many changes were made for the 1971 model year that problems were bound to happen. Of course, the engine not being able to fit in the frame was a big one. But another big one was the seat height. At 34-1/2", it was very tall, so tall that few riders could touch the ground flat-footed. By 1972, the rear of the frame was altered to drop it to 32-1/2". Other problem areas were the thin wire fender stays & headlight bracket. They broke under vibration, despite their rubber mounts. And, the cool new conical hub brakes never worked as well as the units they replace. As an interesting sidenote, parent-company BSA made the decision to make the new oil-bearing frame common to both the Triumph 650 twins & the BSA 650 twins. The Triumph frames were painted black & the BSA frames were dove gray. Some people didn't like the look of the gray frames, but I thought they looked good. BSA's were never very pretty bikes, but the 1971-72 A65s looked nice.


1971 Triumph TR6 SPECIFICATIONS:



MODEL DESIGNATIONS:
1971 Triumph TR6R................................ Low pipes
1971 Triumph TR6C................................ High Pipes
1971 Triumph TR6P................................ Police
1971 Triumph TR6RV............................... 5-speed

ENGINE:
Engine type....................................... OHV vertical twin
Horsepower at RPM............................ 47 BHP @ 6,700 rpm
Bore................................................ 71mm / 2.79"
Stroke............................................ 82mm / 3.23"
Displacement...................................... 649cc / 40 cu. in.
Compression Ratio................................. 8.5:1
Valve Clearance (cold):
Inlet............................................. 0.05mm / 0.002"
Exhaust........................................... 0.10mm / 0.004"
Valve Timing:
Inlet Valve Opens................................. 34 degrees BTDC
Inlet Valve Closes................................ 55 degrees ABDC
Exhaust Valve Opens............................... 55 degrees BBDC
Exhaust Valve Closes.............................. 34 degrees ATDC

IGNITION:
Contact Breaker Type............................... Lucas 6CA
Ignition Breaker Gap............................... 0.4mm / 0.015"
Spark Plug Type.................................... Champion N3
Spark Plug Gap..................................... 0.64mm / 0.025"
Timing (static).................................... 14 degrees BTDC
Timing (fully advanced):........................... 38 degrees BTDC

CARBURETOR (1):
Type............................................... Amal Concentric R930/60
Throat Size........................................ 30mm
Main Jet........................................... 230
Needle Jet......................................... 106
Needle Position.................................... 2
Needle Type........................................ 622/124
Throttle Valve Cutaway............................. 3-1/2
Pilot Jet.......................................... 25

TRANSMISSION:
Gear Ratios, 4-speed:
4th - Top.......................................... 5.84
3rd - Third........................................ 6.76
2nd - Second....................................... 8.17
1st - Bottom....................................... 11.8
Gear Ratios, 5-speed:
5th - Top.......................................... 4.95
4th - Fourth....................................... 5.89
3rd - Third........................................ 6.92
2nd - Second....................................... 9.07
1st - Bottom....................................... 12.78

CLUTCH:
Type............................................... Multi-plate, wet
Number of Plates:
Drive Plates....................................... 6
Driven Plates...................................... 6

SPROCKETS:
Engine............................................. 29 teeth
Clutch............................................. 58 teeth
Gearbox............................................ 19 teeth
Rear Wheel......................................... 46 teeth

CHAIN:
Primary, pitch..................................... 3/8" duplex
Primary, length.................................... 84 links
Final Drive, pitch................................. 5/8" X .400" X 3/8"
Final Drive, length................................ 106 links

CAPACITIES:
Fuel (US versions)................................ 3 Imp. gal.
Fuel (UK & export versions)........................ 4 Imp. gal.
Oil Tank........................................... 4 pints / 2 L
Gearbox........................................... 1 pt / 500cc
Primary Chaincase............................. 1/4 pt / 150cc
Front Forks....................................... 6.4 oz. / 190cc

TIRES:
Front............................................... 3.25 X 19"
Rear................................................ 4.00 X 18"

SUSPENSION:
Front............................................... Telescopic Forks
Rear................................................ Swing Arm

BRAKES:
Front............................................... 8" / 20.32cm TLS
Rear................................................ 7" / 17.78cm SLS

DIMENSIONS:
Seat Height...................................... 34.5" / 87.3cm
Wheelbase........................................ 56" / 142cm
Length.............................................. 87.5" / 222cm
Width............................................... 29" / 73.5cm
Ground Clearance.............................. 7" / 18cm
Weight, unladen................................ 383 lbs / 173.9kg


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TALES OF TRIUMPHS & THE MERIDEN FACTORY

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