1972 TRIUMPH TR6


1972 triumph tr6, triumph tr6, triumph tr7, triumph bonneville, triumph motorcycles

The 1972 Triumph TR6 was the 'sister-bike' (or as some would prefer, 'the little brother') to the 1972 Triumph Bonneville pictured here. Save the twin carbs, side covers & emblems, and the color combo, the Triumph TR6 was virtually identical to the Bonneville. Unfortunately, no photo was available of a '72 TR6, so we had to make do with this Bonnie. However, if you own a '72 TR6, please send us pictures of YOUR BIKE.


1972 TRIUMPH TR6 BY THE NUMBERS
1972 was the second year for the Oil-in-Frame. There were four models for 1972: TR6R (the standard Roadster with low pipes); TR6C (with high pipes running along the left side); TR6P (Police version); and TR6RV (a Roadster with optional 5-speed gearbox). Engine & frame numbers ran from JG033084 to EG057252, built from August 20, 1971 to May 17, 1972. The paint color combinations were Polychromatic Blue & Cold While with black lining. The mudguards (fenders) were also painted blue. This was the last year for the Triumph TR6C (the last one to roll off the assemby line was #AG044359.)

ENGINE CHANGES
The new Quaif-derived 5-speed gearbox became optional starting with engine #CG051405, with a "V" added to the end of the model designation. Full-width cam gears were fitted for quieter operation. Starting with engine #XG043810, the cylinder heads were modified to accept a 'push-in' exhaust pipe fitting. Gone were the threaded-in steel flanges which the pipes clamped to. In their place was a new system (presumably designed to save money) that caused all sorts of problems. The heavy engine vibration worked the steep pipes against the soft aluminum heads & 'hogged-out' the holes so that they would wobble around & fail to seal. The solution was to machine threads into the exhaust ports to install the old-style screw-in spigots & clamp the pipes to them, ala 1971 & earlier. I know, because I did this exact same fix on my 1973 TR7 cum Bonneville Cafe Racer, "The Yellow Bike". Starting with #XG043810, new style rocker boxes were fitted which replaced the 4 small screw-in caps with 2 large cover plates, which greatly aided in valve adjustment. Starting with #AG046174, the cylinder head bolts were changed from a hex-head design to an Allen-head that that allowed the top end to be re-torqued without removing the rocker boxes.

1972 triumph tr6, triumph tr6 tiger, triumph tr7, triumph bonneville, triumph motorcycles

Again this lovely 1972 Triumph Bonneville sits in for our missing 1972 Triumph TR6 photo model.


GEARBOX MODS
The leaf spring used for indexing the shift cam was replaced with a spring-loaded plunger, as before 1970. Starting with #EG056421, the high gear bearing on the 5-speeds was changed from a 13-roller to an 11-roller, which required a new 5th gear & these are not interchangeable with the old ones. Starting with #CG051405, the clutch shock absorber inner & outer plates were secured by 3 through-bolts, now peened over to prevent loosening.

FRAME IMPROVEMENTS
The new oil-bearing frame introduced in 1971 was not without its problems. A good overall design, it simply wasn't well-engineered by parent-company BSA's "brain trust" at Umberslade Hall, the overly expensive tech center BSA had lavished its dwindling resources on. This new design center was supposed to save the company, when in fact, it hurried its demise. Among the many foibles they made was to make the seat height of the new 1971 oil-bearing frame a staggering 34-1/2 inches from the deck. Too tall for most riders. This was remedied for the 1972 Triumph TR6 with an extensive redesign of the rear frame & all the ancillaries that went with it (side covers, thinner seat, air filters, battery tray, electrical suite, all of it). This dropped the seat a full 2 inches, to 32-1/2 inches. The new seat now hinged from the left, like it was back in 1970. The rear Girling shock absorbers (suspension units) went from 12.9 inches to 12.4. All of these mods were made starting with #CG051405.

CYCLE GEAR
Early 1972 Triumph TR6 models had lower front fork sliders with a rough-cast finish & a 'styling rib' running vertically down their sides. Later '72's got polished lower sliders with no styling rib, a much cleaner look. The front fenders (mudguards) got an extra stay to fight vibration & UK models got a lengthened front fender. The handlebar switch consoles were swapped left-to-right so that now the Left console had directional indicators (turn signals), the the kill switch; and the Right now had the headlight flasher button, horn & headlight dimmer (low & high-beam).

triumph conical hubs, triumph conical brakes, triumph motorcycles, triumph tr6, triumph tr7

COOL CONICAL HUBS
New for the 1971 model year, Triumph introduced these gorgeous conical brake hubs, front & rear, with all new brake hardware. The 8-inch fronts were a TLS (Twin Leading Shoe) design that proved to be nowhere near as effective as the 8" TLS unit it replaced. The pivot arms & cams had poor leverage & being conical in shape, they were not full-width as were the earlier designs. The rear was a 7-inch SLS (Single Leading Shoe), which also had leverage problems. These glitches were sorted out over the 2 model years 1971 & 1972, before the front drums were replaced in 1973 with a long-awaited front disk brake (just 5 years after Honda). One must wonder why they spent what little money they had designing an entirely new front brake when they knew they were going to replace it in a couple of years. Why not just come out with the disk brake in 1971? Alas, we may never know. However, the upside to all this is that we have lots of gorgeous conical hubs running around today, and while they may not be the most effective stopping devices, they are awfully pretty!!



MODEL DESIGNATIONS:
1972 Triumph TR6R................................ Low pipes
1972 Triumph TR6C................................ High Pipes
1972 Triumph TR6P................................ Police
1972 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


SAVE THE BONNEVILLE!
Did you ever wonder what really happened to Triumph? This is the behind-the-scenes story of the Meriden Workers' Co-op, written by John Rosamond, the welder-turned-Company Chairman. From the factory takeover in '73, and the formation of the Co-op in '75, through their endless struggles to continue to produce Triumph Bonnevilles, despite constant setbacks & opposition, until its slow death in 1983. The book is loaded with amazing photos & information you won't find anywhere else. This is not hearsay either, this is the real deal right from the source. I lived through this stuff myself, working as an apprentice mechanic in a Triumph/BSA/Norton dealership in 1971 when the first Oil-in-Frame Triumphs arrived to a lukewarm response. There were lots of ups & unfortunately more downs for the cash-strapped Co-op, but the scrappy Brits soldiered on & even came out with some stunning new models (like the Diana watercooled DOHC 4-valve twin, the contra-rotating balance shaft Bonneville, the 8-valve TSS, Anti-Vibration frames with rubber engine mounts & more), all outlined in the book. It's a MUST READ for anyone who mourns the loss of the British Motorcycle Industry as a whole & of Triumph in particular.


You can order the book by clicking on the picture of the book cover, above.


MORE TRIUMPH MOTORCYCLE BOOKS


TALES OF TRIUMPH & MERIDEN

TRIUMPH MOTORCYCLES: TRIUMPH ENGINEERING CO.

TRIUMPH WORKSHOP MANUAL, 1935-1939

TRIUMPH WORKSHOP MANUAL, 1937-1951

TRIUMPH WORKSHOP MANUAL, 1945-1955

TRIUMPH MOTORCYCLES: FROM SPEED TWIN TO BONNEVILLE

TRIUMPH MOTORCYCLES - HINKLEY RENAISSANCE

SAVE THE TRIUMPH BONNEVILLE

THE INSIDE STORY OF THE MERIDEN WORKERS' CO-OP.
STORY OF THE TRIUMPH BONNEVILLE - MOVIE

TRIUMPH 650 & 750 TWINS

ESSENTIAL BUYERS GUIDE TO TRIUMPH BONNEVILLE

TR BONNEVILLE 2001-08

TR BONNEVILLE, PORTRAIT OF LEGEND

TR BONNEVILLE: T120/T140

TRIUMPH MC RESTORATION

HAYNES TR TRIPLES & FOURS

TRIUMPH 21 TO DAYTONA

TRIUMPH TIGER CUB BIBLE

For more Great Books, please visit our
MOTORCYCLE BOOK STORE




HOME PAGE
Triumph Motorcycles
BSA Motorcycles
Norton Motorcycles
Matchless-AJS Motorcycles
AMC-Associated Motor Cycles
Royal Enfield Motorcycles
Ariel Motorcycles
Vincent Motorcycles
Velocette Motorcycles
Rickman Motorcycles
Japanese Motorcycles
Cafe Racers
Choppers & Bobbers
Rat Bikes
Classic Racing Motorcycles
Classic Motorcycle Auctions
Classic Motorcycle Shows
Classic Motorcycle Rides
Classic Motorcycle Restoration
Classic Motorcycle Shops
Classic Motorcycle Clubs
Classic Motorcycle Photo Gallery
Classic Motorcycle Events Calendar
Send us Pictures of YOUR BIKE
YOUR BIKE Pictures
About Us
Site Map
CONTACT US
Brit Iron Back Issues
Visit our STORE
Subscribe to our FREE e-zine & get a FREE 11X17 Poster
BACK TO TOP - 1972 Triumph TR6


1972 Triumph TR6
1/1/14




Classic Triumph
2014 Wall Calendar


Historic Motorcycles
2014 Wall Calendar


Vintage Motorcycles
2014 Wall Calendar


More CALENDARS