1958 TRIUMPH TR6


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This 1958 Triumph TR6 Trophy features the optional twin high pipes, very popular in the US Market, which could replace the 2-into-1 side exhaust.



1958 TRIUMPH TR6 BY THE NUMBERS
1958 Engine/Frame Numbers: 011861 to 019244
Production Dates: October 10, 1957 to June 25, 1958

ENGINE CHANGES
Early Delta Heads were prone to cracking around the valve seats. It was deemed prudent to reduce the sizes of the intake (inlet) and exhaust valves to increase the amount of material around the seats. Intakes went from 1-19/32" to 1-1/2", and exhausts dropped from 1-7/16" to 1-11/32". The combustion chamber was reconfigured to suit. While this may have cured the cracking problem, the smaller valves hurt performance. Because of this, the early Delta heads with the bigger valves remained popular with racers. Despite this, however, performance continued to increase until crankshafts began snapping. Until then, the pre-unit 650 twins all used 3-piece pressed-together (built-up) crankshafts. A new, one-piece forged steel crank was introduced in 1958, along with a stronger clutch.

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BONNEVILLE IS COMING
As an interesting sidenote, it was the availability of the new one-piece crank, the Delta Head in twin-carb configuration, & the crazy demand in America for more & more speed that lead to, indeed made inevitable, the arrival of the Triumph Bonneville in 1959.

FRAME & RUNNING GEAR CHANGES
The new 8-inch front brake now became a full-width hub with a chromed & louvered end cover. The backing plate now locked into a lug in the fork tube. The front spokes increased in size to match the larger rear spokes. The front forks now had new sliders with more substantial brazed lugs supporting a new central front fender (mudguard) mount, dispensing with front stays, though the rear stays remained. The oil cap was moved to a more upright position so as not to foul the leg when kickstarting. A new anti-theft head steering lock was introduced.

A CRAZY NEW GEARBOX
Triumph Motorcycles thought it wise to introduce to the world its new "Slickshift" mechanism, that allowed clutchless shifts. It never worked very well & was a flop. The driveside chaincase was modified to accept a new oil seal aimed at stopping oil transfer between the crankcase & the primary. Also a new rubber sleeve was installed on the kickstart shaft to try to stem oil leakage.


1958 Triumph TR6 SPECIFICATIONS:




MODEL DESIGNATIONS:
1958 Triumph TR6A/B Trophy.................... Street Scrambler

ENGINE:
Engine type....................................... OHV vertical twin
Horsepower at RPM............................ 42 BHP @ 6,500 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 BTDC
Exhaust Valve Opens.......................... 48 degrees BTDC
Exhaust Valve Closes.......................... 27 degrees BTDC

IGNITION:
Spark Plug Gap.................................. 0.50mm / 0.020"
Timing (fully advanced):
Crankshaft position............................. 38 degrees BTDC
Piston position................................... 11mm / 7/16" BTDC

CARBURETOR:
Type................................................ Amal Monobloc

TRANSMISSION:
Speeds.............................................. 4
Gear Ratios:
4th - Top........................................... 4.6
3rd - Third......................................... 5.5
2nd - Second....................................... 7.8
1st - Bottom...................................... 11.2
RPM @ 10MHP in Top Gear................... 638 RPM

CLUTCH:
Type................................................ Multi-plate, wet
Number of Plates:
Drive Plates...................................... 6
Driven Plates.................................... 5
Friction Material................................ Neolangite

SPROCKETS:
Engine............................................. 21 teeth
Clutch............................................. 43 teeth
Gearbox.......................................... 18 teeth
Rear Wheel...................................... 43 teeth

CHAIN:
Primary, pitch.................................. 1/2" X .335" X 5/16"
Primary, length................................. 70 links
Final Drive, pitch............................... 5/8" X .400" X 3/8"
Final Drive, length............................. 101 links

CAPACITIES:
Fuel (US versions)............................. 3 Imp. gal.
Fuel (UK & export versions)................. 4 Imp. gal.
Oil Tank........................................... 5 pints / 3 L
Gearbox........................................... 2/3 pt / 400cc
Primary Chaincase............................. 1/4 pt / 150cc
Front Forks....................................... 1/4 pt / 150cc

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

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

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

DIMENSIONS:
Seat Height...................................... 30.5" / 77.5cm
Wheelbase........................................ 55.25" / 140.3cm
Length.............................................. 86.25" / 219cm
Width............................................... 28.5" / 72cm
Ground Clearance.............................. 5" / 12.7cm
Dry Weight, unladen............................ 380 lbs / 173kg


TRIUMPH MOTORCYCLE BOOKS


TRIUMPH RESTORATION, PRE-UNIT

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




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