1970 Triumph TR6
1970 TRIUMPH TR6 BY THE NUMBERS
For 1970, the Triumph TR6 was again known as “Tiger”, as the single carb twin would continue to be known, even beyond the switch from 650 to 750. But for the 1970 model year, there were 4 models in the TR6 lineup: The standard TR6, Roadster TR6R, Competition TR6C & the Police TR6P. Engine & Frame Numbers ran from HD23795 & ND60540, built from July 9, 1969 to October 8, 1970. This is the last year before the controversial & devastating switch over to the oil-bearing frame in 1970. It just got worse from there.
The conversion from British Standard (CEI) threads to Unified or ‘American’ (UNC & UNF) threads was completed. A new breather system was devised, eliminating the timed breather at the end of the intake cams. Three holes were drilled in the drive-side crankcase below the mainbearing housing, maintaining a constant oil level in the primary case, the driveside mainbearing oil seal was deleted, a breather pipe was installed at the upper-rear of the primary case & from then on for the rest of its life, the engine breathed through the primary. A hose attached to the breather pipe ran all the way to the back to the rearmost of the rear mudguard (fender) where it vented to the open air. Starting with Engine #AD39329, the Amal R930/45 Concentric carburetor was replaced with the R930/23 with cast-in weir & drain plug. Jets & settings remained unchanged. Smaller Lucas 17M oil-filled 12-volt ignition coils were now specified across all models.
At Engine #GD53756, the 1970 Triumph TR6 got aluminum bronze selector forks with captive steel rollers to replace the old forged steel units. A new precision-pressed camplate got a locating spring-loaded plunger instead of the old leafspring.
FRAME & CYCLE GEAR Staring with #JD26050, the front engine mount became a detachable plate for ease of assembly. The Girling rear shocks (suspension units) were now fitted with castellated spring adjuster sleeves. Starting with #AD39329, the fork sliders changed from wheel spindle cap bolts to studs & nuts. The mudguard (fender) stays were now welded on with captive square nuts. The steering damper was deleted. The rear brake stay, formerly tubular, was changed to flat stock.
ABOVE: 1970 Triumph TR6C Street Scrambler with high pipes running along the left side.
Starting with the 1970 Triumph TR6, the rear chain oiling system, essentially an adjustable ‘oil leak’ fed by the oil tank, was eliminated because…why else?…it leaked! It would leave puddles on the ground & there were too many of them already. The front fender (mudguard) got a new bottom stay & the rear fender was modified to accepted the “D”-section breather hose which ran along its left side. The rear grabrail was now integral with the rear fender stay. A new seat pan lowered seat height. The speedometer was changed again to a SSM/00 & the tachometer (rev counter) to an RSM 3003/13.
BELOW: The right side of the ’70 TR6C above. Note how much ground clearance is created by routing the pipes high, like they did.
1970 Triumph TR6 SPECIFICATIONS
Bore & Stroke
Air-cooled OHV vertical twin
649cc / 40.0 ci
71mm X 82mm / 2.79″ X 3.23″
1- Amal Concentric, 30mm
Battery & coil, Lucas
42 bhp @ 6500 rpm
3/8″ triplex chain X 84 links
Engine 29T X Clutch 58T
4-speed constant-mesh, right-foot shift
5/8″ X .400″ X 3/8″ chain X 106 links
Gearbox 19T X Rear 47T
Brazed lug, full-cradle, single downtube
Telescopic fork, hydraulic damping
Swing arm, 2 Girling dampers
8″ SLS drum, full-width
7″ SLS drum, one-side
3.25″ X 19″ Dunlop
4.00″ X 18″ Dunlop
2.5 Imp gal (US)/4 Imp gal (UK & export)
54.5″ / 140.3 cm
32.5″ / 77.5 cm
5.0″ / 12.7 cm
380 lbs / 173 kg