Post-World War II, Triumph’s larger twins remained recognizably similar to the first Speed Twin of 1938. But as the 1960s dawned, unitary construction of engine and gearbox, already a feature of the 350 and 500 twins, was applied to the 650s, launching in the 1963 model year. The café racer’s favourite since its launch, thanks to lusty acceleration and a top speed approaching 120mph, the Bonneville continued in this new form as Triumph’s top-of-the-range sportster. Adjustments to frame design and general specifications over the years, included standardized 12-volt electrics, shuttle-valve fork internals, independently adjustable ignition points, Amal Concentric carburettors and a long overdue twin-leading-shoe front brake. The Bonnie continued essentially unchanged, before the launch of the ‘oil-in-frame’ models in 1970.
The 1970 Triumph T120R Bonneville on offer here comes to us from a Southern California collector/restorer/racer/land speed record holder in various classes and all-round enthusiast. The bike was fully restored from the ground up in his extensive and clinical workshop. Starting at its heart, the engine features new main bearings, rod bearings, wrist pin bushings, rebore with 0.020 pistons, new rings, valves, valve guides and springs. The head was milled, tappets resurfaced, and a megacycle cam and Morgo oil pump installed.
A new clutch was installed with new primary chain and cushdrive rubbers. The gearbox was overhauled with new bearings, seals and cam plate.
Air and fuel are mixed in a pair of Amal MkI 930 carbs and the charging system features a 200W stator and new regulator and rectifier. New coils were installed with a Pazon Electronic Ignition for added reliability.
This is all housed in a restored, matching numbers frame with new swingarm bushings and steering head bearings. Up front are rebuilt forks with new bushings, seals and springs, while a new pair of Hagon shocks reside at the rear. New wheel rims with stainless spokes are shod with new tires. A new chain was installed.
The paint is exquisite, applied professionally. Brightwork is fresh and a new seat provides a good place to sit with a nice view of the new gauges.
The bike starts readily, idles smoothly and rides exceptionally well. With 421 miles on the odometer siren the comprehensive restoration, the bike has been re-torqued and further dialed in, ready for its new rider.
Engine no. T120R PD33179
Frame no. T120R PD33179
Location: Lancaster, California