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


Check out these TRIUMPH BOOKS


TRIUMPH BONNEVILLE YEAR-BY-YEAR

TRIUMPH BONNEVILLE ESSENTIAL BUYER’S GUIDE

COMPLETE BOOK OF CLASSIC & MODERN TRIUMPHS

TRIUMPH MOTORCYCLES 1956-1983

FACTORY-ORIGINAL TRIUMPH TWINS

TRIUMPH MOTORCYCLES

TRIUMPH MOTORCYCLE RESTORATION, PRE-UNIT

TALES OF TRIUMPHS & THE MERIDEN FACTORY

TRIUMPH ILLUSTRATED SHOP MANUAL, 1935-1939

TRIUMPH ILLUSTRATED SHOP MANUAL, 1937-1951

TRIUMPH ILLUSTRATED SHOP MANUAL, 1945-1955


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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1974 Triumph Bonneville
12/12/14

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