1959 Triumph Bonneville

ABOVE: The 1959 Triumph Bonneville had the big fenders and nacelle of the Triumph Thunderbird. Not a popular move with Americans, many of whom swapped it out for the more svelte TR6 bodywork.

ALL NEW BIKE
When it was introduced, the 1959 Triumph Bonneville 650 was one of, if not THE fastest motorcycles you could buy. It was a real hot rod! The new T120 designation is supposed to suggest that it could do 120 mph! Actual road tests done by motorcycle magazines of the day topped-out a box-stock '59 Bonnie at 108 mph. Not quite 120, but very fast for 1959! This was the only year with no letter designation after the T120.

LOOK NOT QUITE RIGHT
Production of the new T120 began at Triumph Motorcycles Meridan plant on September 4, 1958 with Engine #020377. All 1959 Bonnevilles came in Pearl Grey and Tangerine, a color combo that didn't play well in America. Another thing the Yanks didn't like was the 'bodywork'. Triumph had styled the new 1959 Triumph Bonneville more closely to the Thunderbird, with a headlight nacelle and full fenders. It was better suited to rainy England where good weather protection and ease of cleaning were important. What America wanted was a stripped-down street racer like the TR6. By 1960, Triumph addressed ABOVE: 1959 Triumph Bonneville - Big fenders & nacelle of the Triumph Thunderbird.



ALL NEW BIKE
When it was introduced, the 1959 Triumph Bonneville 650 was one of, if not THE fastest motorcycles you could buy. It was a real hot rod! The new T120 designation is supposed to suggest that it could do 120 mph! Actual road tests done by motorcycle magazines of the day topped-out a box-stock '59 Bonnie at 108 mph. Not quite 120, but very fast for 1959! This was the only year with no letter designation after the T120.

LOOK NOT QUITE RIGHT
Production of the new T120 began at Triumph Motorcycles Meridan plant on September 4, 1958 with Engine #020377. All 1959 Bonnevilles came in Pearl Grey and Tangerine, a color combo that didn't play well in America. Another thing the Yanks didn't like was the 'bodywork'. Triumph had styled the new 1959 Triumph Bonneville more closely to the Thunderbird, with a headlight nacelle and full fenders. It was better suited to rainy England where good weather protection and ease of cleaning were important. What America wanted was a stripped-down street racer like the TR6. By 1960, Triumph addressed this.

HOT ROD BONNEVILLE
How do you build a hot rod? They stared with a T110 engine (already fast), added a high-lift E3134 inlet cam and a E3325 exhaust cam, bigger valves (1-1/2" inlet, 1-1/32" exhaust) porting and polishing, higher compression (8.5:1), stronger pistons, a strengthened, one-piece forged crankshaft (EN16B) with bigger 1-5/8" journals and ball bearings at both ends. Fitment of a new 2-1/4" wide flywheel dropped the balance factor from 70% to 50%. Crankshaft balance factors would rise and fall over the years, in an effort to combat vibration. The vertical twin had started out with 500cc and 26 hp, and vibration wasn't much of an issue. But now, it was up to 650cc and pumping out 46 hp at 6500 rpm. Vibration was starting to reel its ugly head and as the quest for more and more power continued, it only got worse. Heavier cranks, lighter cranks, different bearings, balance factors all the way up to 81% came and went, but the vibration never left.

BIG CARBS
This new fire-breathing engine was fed by two 1-1/16" Amal Monobloc carburetors that shared a common, remote float bowl (Amal 14/617) that was mounted to the frame. This proved unsatisfactory as many owners experienced fuel starvation and stalling under heaving braking. This was soon remedied with the adoption of 'normal' Amal Monobloc carburetors each with their own integral float bowl. The float bowl screws were safety-wired (forming a triangle of wire) to keep them from loosening under vibration. The 'tickler' valve was on the remote float bowl. There were no air filters, just little polished aluminum bellmouths. Main jet size was 240, pilot jet 25 and needle jet 0.1065.

TRANSMISSION
The rest of the 1959 Triumph Bonneville was pure Tiger T110. The 4-speed gearbox, which traced its ancestry back to the original one used in the seminal 1937 Speed Twin, was taken directly from the T110. Inside the primary case, the engine sprocket had 24 teeth and the clutch sprocket 43, with a 70-link endless 1/2" X 5/16" single-row chain, tensioned by pivoting the transmission in its mounts. Final drive was by 101-link 5/8" X 3/8" chain with a 18-tooth front sprocket and a 46-tooth rear wheel sprocket.

IMPROVED CLUTCH
The added power brought about by the twin carbs and all the other 'hot rod mods' (the Tiger made 40 hp to the 1959 Triumph Bonneville's 46) proved to be more than the overtaxed clutch could handle. So, this too was upgraded with a new Neolangite friction surface on its 6 drive and 5 driven plates, and the clutch center was hardened.

FRAME
The 1959 Bonneville's frame is identical to that of the 1959 Tiger T110. Introduced on the 1954 T110, the rear swing arm was poorly supported in the frame and tended to flex, earning it the nickname "Whip Iron", due to its tendency to wobble and weave. This would be remedied in 1960 with the adoption of the new, and much-reviled 'duplex frame', which solved the swing arm issue, but brought with it a whole new set of problems.

RUNNING GEAR
The footpegs attached direction to the engine mounting plates, bewteen the engine and tranny, with the left one passing through the primary case (not good if you dropped it on that side, eh>). Rear shocks were fully-enclosed Girlings with 100 lb/ft spring tension and adjustable pre-set. The telescopic forks were straight off the 6T/T110 line. The bike sat on a 55-1/4" wheelbase with a 64-1/2 degree steering head angle. The frame was made by sweating or brazing steel tubes into cast lugs, which was standard practice for the day. Welded frames came much later.

WHEELS & BRAKES
Also shared with the T110 were wheels and brakes. The front was an 8" full-width single-leading-shoe (SLS) unit, laced with 40 identical 8/10G X 5-5/8" cadmium-plated spokes to a 19" chromed WM2-19 rim fitted with a 3.25 X 19 Dunlop ribbed tire. The standard rear wheel had a 7" cast iron drum with SLS brake, laced (with 8/10G X 8" spokes on the left, and 8/10G X 8-3/8" on the right, all with right-angle nipples) to another WM2-19 (identical to the front) chromed rim steel rim with a 3.50 X 19 Dunlop Universal tire. There was also an optional Quickly Detachable (QD) rear wheel that allowed for fast and easy rear wheel removal with very few tools.
SEAT
There were two seats offered for the 1959 Triumph Bonneville, but its unsure when the changeover was made. The first ones came with the Tiger 110s dual seat, later ones with a slimmer 'sports' seat from the Trophy models. Both were covered in waterproof black "Vynide" with white piping. Some of the later versions also had gray trim around the bottom edge. California-bound bikes needed a safety strap, by law, so a kit was provided and installed by the dealer.

BODYWORK
But it was the sheet metal, the 'bodywork' that was most controversial. Most Americans were put off to the fully valanced fenders, since they do very little riding in the rain, and they just looked out of place on such a sporting bike. Almost all 1959 Triumph Bonneville were painted the same, but a few very late '59 UK and export machines went out with Azure Blue replacing the Tangerine. The fenders were painted in Pearl Grey with a Tangerine (orange) stripe running down the center, following a longitudinal raised section. The two colors were separated by a lovely gold pin-stripe (hand striped by craftsmen). The 5 qt. oil tank was on the right side, with a matching battery and tool box on the left. Both were painted Pearl Gray, although some very early UK/Exports were black. The oil tank had a gold transfer about halfway up indicating proper oil level, and the tool box had a small gold "Bonneville 120" transfer on it. The all steel, welded tank held 4 Imperial-gallons in the UK and most export markets, but the US got a smaller 3-Imperial gallon unit. The top half was painted Pearl Gray and the bottom half Tangerine, separated in various places on the tank, by chrome trim, the knee pads, and gold striping. The Triumph tank badge is quite large and impressive. The famous 'Grille Badge' features the classic gold-accented Triumph logo over a forward-leaning chrome grille with 11 vertical stays and 7 horizontal ones, bracketed on top and bottom by streamlined, high-stylized chromed 'eyebrows'. GORGEOUS! Triumph certainly knew how to build a pretty motorcycle!

1959 Triumph T120 Bonneville
SPECIFICATIONS

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 drive sprockets

Frame Type

Suspension, front

Suspension, rear

Brake, fron

tBrake, rear

Tire, front

Tire, rear

Wheelbase

Seat Height

Ground Clearance

Fuel capacity

Dry weight

Air-cooled OHV vertical twin, non-unit

649cc / 40.0 ci

71mm X 82mm / 2.79" X 3.23"

8.5:1

2- Amal Monobloc 1-1/6"

Lucas magneto

46 bhp @ 6500 rpm

1/2" X .335" X 5/16" chain, 70 links

24T X 43T

Multi-plate, wet

4-speed constant mesh, right foot shift


11.9:1

8.25:1

5.81:1

4.88:1

5/8" X .400" X 3/8" chain, 101 links

18T X 46T

Brazed lug, rigid

Telescopic fork, hydraulic damping

Swing arm, 2 Girling dampers

8" SLS drum

7" SLS drum

3.25" X 19" Dunlop

4.00" X 18" Dunlop

55.25" / 140 cm

30.5" / 77 cm

5" / 12.7 cm

3 Imp gal (US); 4 Imp gal (UK & export)

404 lbs / 183 kg


MORE TRIUMPH BONNEVILLES:
Triumph Bonneville
Triumph Bonneville Pre-Unit (1959-1962)
.....1959
.....1960
.....1961
.....1962
Triumph Bonneville, Unit-Construction(1963-1970)
.....1963
.....1964
.....1965
.....1966
.....1967
.....1968
.....1969
.....1970
Triumph Bonneville, Oil-in-Frame
.....1971
.....1972
.....1973
.....1974
.....1975
.....1976
.....1977
.....1978
.....1979
.....1980
.....1981
.....1982
.....1983
Les Harris Bonnevilles(1983-1989)
OTHER TRIUMPHS:
Triumph TR6
Triumph TR7
Triumph Trophy
Triumph Tiger
Triumph Thunderbird
Triumph Trident
Triumph X-75 Hurricane


Check out these TRIUMPH BOOKS

COMPLETE BOOK OF CLASSIC & MODERN TRIUMPHS


TRIUMPH MOTORCYCLES IN AMERICA


TRIUMPH MOTORCYCLE RESTORATION


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


TRIUMPH BONNEVILLE YEAR BY YEAR


TRIUMPH TRIPLES


TRIUMPH RACING MOTORCYCLES IN AMERICA


TRIUMPH MOTORCYCLES


TRIUMPH, by Roy Bacon


TRIUMPH 750/900 TRIPLES & 1200 FOURS 1991-1999, Haynes Repair Manual


TRIUMPH TROPHY BIBLE


TRIUMPH DAYTONA, SPEED TRIPLE SPRINT & TIGER: 885/955 1997-2005, Haynes Repair Manual


BSA & TRIUMPH TRIPLES GOLD PORTFOLIO 1968-1976


TRIUMPH TRIDENT OWNERS WORKSHOP MANUAL, by Haynes


TRIUMPH: A CENTURY OF PASSION & POWER


TRIUMPH BONNEVILLE, by Osprey


TRIUMPH TIGER 100 & 110, 1939-1961, by Roy Bacon


TRIUMPH TIGER 100 & DAYTONA


TRIUMPH BONNEVILLE, by Crowood


TRIUMPH by Don Morley


TRIUMPH TRIPLES & FOURS 1991 & 2004


TRIUMPH 350 & 500 1957-1974 ESSENTIAL BUYERS GUIDE


BONNIE: THE DEVELOPMENT OF THE TRIUMPH BONNEVILLE


TRIUMPH SINGLES: EARLY DAYS TO 1974, by Roy Bacon


TRIUMPH: RETURN OF THE LEGEND


TRIUMPH FUEL INJECTED TRIPLES 1997-2000


BOOK OF TRIUMPH TWINS 1968-1969, by Floyd Clymer


THE TRIUMPH STORY: RACING & PRODUCTION MODELS 1902-PRESENT


TRIUMPH 350 & 500 TWINS 1958-1973, Haynes Repair Manual


TRIUMPH BONNEVILLE 2001-=2008 ROAD TEST PORTFOLIO


HINKLEY TRIPLES & FOURS


TRIUMPH PRE-UNIT TWINS


HINKLEY TRIUMPHS: THE FIRST GENERATION


TRIUMPH BONNEVILLE BIBLE: ALL MODELS 1959-1983


TRIUMPH TWENTY-ONE TO DAYTONA: C CLASS 350 & 500 TWINS


ORIGINAL TRIUMPH BONNEVILLE


TRIUMPH 650 & 750 TWINS


TRIUMPH MOTORCYCLES & CUSTOM BIKES


TRIUMPH MOTORCYCLES


TRIUMPH, THE LEGENDS SERIES


TRIUMPH THUNDERBIRD SUPER PROFILE


TRIUMPH SPEED TWIN & THUNDERBIRD BIBLE


TRIUMPH BONNEVILLE T120/T140


TRIUMPH MOTORCYCLES FROM 1950-1983


TRIUMPH & BSA TRIPLES: THE COMPLETE STORY


TRIUMPH THUNDERBIRD, TROPHY & TIGER ESSENTIAL BUYERS GUIDE


TRIUMPH TIGER CUB BIBLE


ROAD RACING HISTORY OF THE TRIUMPH 500 UNIT TWIN


EDWARD TURNER: THE MAN BEHIND THE MOTORCYCLES


SAVE THE BONNEVILLE: THE INSIDE STORY OF THE MERIDEN WORKERS CO-OP


TRIUMPH DAYTONA 1991-2006 ROAD TEST PORTFOLIO


TRIUMPH DAYTONA 2003-2009 ROAD TEST PORTFOLIO


TRIUMPH TIGER 100 / DAYTONA: DEVELOPMENT HISTORY


TRIUMPH, by Daniel Gilpin


BOOK OF TRIUMPH MOTORCYCLES ILLUSTRATED SHOP MANUAL 1935-1939


TRIUMPH: THE RACING STORY


TRIUMPH BONNEVILLE T120 1959-1974, by Roy Bacon


TRIUMPH BONNEVILLE GOLD PORTFOLIO 1959-1983


TRIUMPH TRIDENT SUPER PROFILE


ILLUSTRATED TRIUMPH BUYERS GUIDE, by Roy Bacon






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