1974 TRIUMPH BONNEVILLE


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Since so few 1974s are in existence, we had to make due with this lovely 1973 Triumph Bonneville. Other than color (Astral Red was actually a Canadian color combo), this '73 looks just like a '74.




SHORT MODEL YEAR
The 1974 Triumph Bonneville was built in very low numbers. It was a very odd year in Triumph Bonneville history. Angry workers hearing of the impending shutdown of the Triumph Motorcycles plant at Meriden, shut it down themselves in protest, in October 1973 just as production was being switched from 1973 models to making 1974s. This affected not just Triumph Bonneville production but also Triumph TR6, TR7, & Triumph Daytona (Tridents were produced at BSA's Small Heath plant, side-by-side with BSA Rocket 3s). Production didn't resume again until 1975, so very few 1974 Triumph Bonneville s were ever produced.

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FEW CHANGES
However, the 1974 Triumph Bonneville model year did begin officially with Engine #GJ55101, but since so few bikes were actually built, the usual rash of mid-year revisions never happened. As the result, one of the very few changes made to the engine were new rocker boxes with two extra bolts on each inspection cover. The slimline tank grew from 2-1/2 US gals to 3.6 US gals. Other than minor detail changes here & there, the only other significant difference from the previous model year was the color schemes, now Cherokee Red over Cold White with Gold pinstriping for the T140, and Purple over Cold White on T120s. Again, the fenders were chromed & only the tank was painted.


1974 Triumph Bonneville SPECIFICATIONS:



MODEL DESIGNATIONS:
1974 Triumph Bonneville T120RV.................... 650cc
1974 Triumph Bonneville T140RV.................... 750cc

ENGINE:
Engine type....................................... OHV vertical twin
Horsepower at RPM............................ 49 BHP @ 6,200 rpm
Bore................................................ 76mm / 2.79"
Stroke............................................. 82mm / 3.23"
Displacement.................................... 744cc / 45 cu. in.
Compression Ratio............................. 8.6:1
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 BTDC
Exhaust Valve Opens.......................... 55 degrees BTDC
Exhaust Valve Closes.......................... 27 degrees BTDC

IGNITION:
Ignition Breaker Gap............................. 0.4mm / 0.015"
Spark Plug Gap.................................. 0.50mm / 0.020"
Timing (static).................................14 degrees BTDC
Timing (fully advanced):........................ 38 degrees BTDC

CARBURETORS:
Type................................................ Amal Concentric
Throat Size....................................... 30mm
Main Jet........................................... 210
Needle Jet........................................ .107
Needle Position.................................. 2
Needle Type.......................................D
Throttle Valve.................................... 2
Pilot Jet............................................ 25

TRANSMISSION:
Speeds.............................................. 4
Gear Ratios:
5th - Top........................................... 4.7
4th - Fourth........................................ 5.59
3rd - Third......................................... 6.58
2nd - Second...................................... 8.63
1st - Bottom...................................... 12.25

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

SPROCKETS:
Engine............................................. 29 teeth
Clutch............................................. 58 teeth
Gearbox.......................................... 20 teeth
Rear Wheel...................................... 47 teeth

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

CAPACITIES:
Fuel (US versions)............................. 2.5 Imp. gal.
Fuel (UK & export versions)................. 4 Imp. gal.
Oil Tank........................................... 5 pints / 3 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............................................... 10" / 12.9cm disk
Rear................................................ 7" / 17.78cm SLS

DIMENSIONS:
Seat Height...................................... 32.5" / 77.5cm
Wheelbase........................................ 54.5" / 140.3cm
Length.............................................. 85.5" / 202cm
Width............................................... 28.5" / 72cm
Ground Clearance.............................. 5" / 12.7cm
Weight, unladen................................ 387 lbs / 176kg


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.


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

Triumph Motorcycles
Triumh Bonneville
Triumph Bonneville, Pre-Unit Construction, 1959-1962
Triumph Bonneville, Unit Construction, 1963-1970
Triumph Bonneville, Oil-in-Frame, 1971-1983

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