Unit Construction Triumph TR6

The Triumph TR6 was introduced in 1956 & as such, like all Triumph twins at the time, it was of Non-Unit (or Pre-Unit) Construction. This meant that the engine package was made up of a separate crankcase, gearbox & primary chaincase, all bolted together with steel plates, in the frame. It was bulky, heavy, prone to flex & expensive to produce & assemble.

Unit Construction refers to the design practice of taking the separate crankcase, gearbox & primary case, then incorporating them into a single set of unitized cases. It was lighter, more compact, stronger (& therefore allowed more power), smoother, cleaner & cheaper to produce & assemble. The Triumph 3TA 350cc twins converted to unit construction in 1957, with the TR5/5TA 500cc twins following in 1959. The big 650 twins were enjoying such success in the late 1950s that Triumph Motorcycles decided to leave well enough alone. So, unit construction wasn't introduced in the Triumph TR6 until the 1963 model year. And it was to remain basically unchanged until the demise of Triumph Motorcycles in the early 1980s.

Unit Construction Triumph TR6

1963 Triumph TR6

First year for the Unit Construction Triumph TR6 plus an all-new frame & running gear. New 9-bolt head. Spark & lights now via alternator, points & coils. TR6S/S is the only TR6 model.

1964 Triumph TR6

Mostly minor changes to correct & perfect design & production flaws in the new engine, frame & running gear. Seal on kickstart shaft, an all-new front fork assembly with external springs, new gauges & a bigger 1-1/8" Amal carb.

1965 Triumph TR6

Some subtle changes for 1965, further developing the unit construction design. New main bearings, some gearbox upgrades & some general improvements to the frame & running gear. Triumph Motorcycles are at their peak during this era.

1966 Triumph TR6

Good news/bad news: We finally get 12-volt electrics, but it comes with a Zener Diode. Oh well. Steering angle steepened for quicker handling. Slim new tank & that famous "Eyebrow" tank emblem.

1967 Triumph TR6

The big news for 1967 is the switch from the age old Amal Monobloc carburetor to the new Amal Concentric. The parcel rack on top of the tank on US models is eliminated. Otherwise, mostly minor changes.

1968 Triumph TR6

The big news for 1968 was the introduction of a new 8-inch TLS (Twin Leading Shoe) front brake to replace the age-old SLS unit. The TR6 got hotter E3134 cams (like the Bonneville). Zener Diode got moved to the front of the bike.

1969 Triumph TR6

The "Tiger" name appears for the first time on a TR6. Gone is the old "Trophy". Gone also are the old British Standard threads (CEI), in favor of Unified or 'American' threads (UNC & UNF). Numerous engine mods aimed at oil tightness & a new tank badge, the "bird wing".

1970 Triumph TR6

The last year before the switch to the dreaded oil-bearing frame. The timed engine breather is ditched in favor of breathing through the primary case, with a hose running out the back fender. Gone is the rear chain oiler.

1971 Triumph TR6

First year for the Oil-in-Frame Triumph TR6. New oil-bearing frame, new forks, new wheels with cool conical hubs, new pipes, new look. Should have been a hit. Small problem - the engine didn't fit in the new frame. Got production off to a late start. The new TR6 never sold as well as the TR6 it replaced.

1972 Triumph TR6

The new oil-bearing frame is too tall, so seat height is lowered a full 2 inches. A 5-speed gearbox becomes available on the TR6RV models (the "V" signifying a 5-speed). Clamp & spigot exhaust fixing is ditched in favor of pipes that simply slip into the head. Bad idea.

1973 Triumph TR7

A big year for Triumph. 650 grows to 750, new TR7 name, 5-speed gearbox is now standard across the line & finally a front disk brake. Many other smaller changes including a new headlight mounting system.
Visit our Triumph TR7 page for more.

Check out these TRIUMPH BOOKS

2018 Classic Triumph Calendar

Triumph Motorcycles: The art of the motorcycle

The Complete Book of Classic and Modern Triumph Motorcycles 1937-Today (Complete Book Series)

Triumph Motorcycles: From Speed-Twin to Bonneville

Triumph Bonneville and TR6 Motorcycle Restoration Guide: 1956-83

British Motorcycles Triumph (Little Books)

Triumph Motorcycles in America

McQueen's Motorcycles: Racing and Riding with the King of Cool

Triumph Motorcycle Restoration

Illustrated Triumph Motorcycles Buyer's Guide: From 1945 Through the Latest Models (Illustrated Buyer's Guide)

Tales of Triumph Motorcycles and the Meriden Factory

Hinckley Triumphs: The First Generation (Crowood Motoclassic)

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Last updated 12/7/17

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