Italian engineer Lino Tonti joined FB Mondial in 1957, when the Milanese factory was top marque in125cc and 250cc Grand Prix racing. But plans he had for 1958 were thwarted when Mondial made a pact with Gilera and Moto Guzzi to jointly withdraw from costly world championship contention. Not to be deterred, Tonti teamed up with redundant Mondial chief race mechanic Giusseppe Pattoni to create the Paton marque. The first Paton, a double-overhead-cam 125cc single, was followed by a 250cc twin. By the time the latter was racing, Tonti had moved on to design and develop similar twins for Bianchi. A big manufacturer of cars, pedal cycles and bearings as well as motorcycles, Bianchi (pronounced ‘bee-anky’) had raced dohc 350cc engines in the 1920s and had a supercharged 500cc inline four ready when World War II began. A return to international motorcycle racing came when seven Tonti-designed six-speed 250cc (55 x 52.5mm) twins were entered for the 1960 Lightweight TT. Practice troubles saw only two start, ridden by Derek Minter, who broke down, and Osvaldo Perfetti who finished ninth. Tino Brambilla raced a 350cc (65 x 52.5) version in the 1960 GP des Nations at Monza, sensationally lapping at 111.35mph (against Gary Hocking’s 111.66mph on his MV four), but failed to finish. Bianchi’s best 1961 GP results were two second places for new works riders behind Hocking – for Bob McIntyre at the Dutch TT and Alistair King in the Ulster, while Brambilla was Italian champion. A 68.4mm bore (386cc) twin for the 500cc class, with four carburettors, appeared at the Italian GP but did not race. In 1962, Silvio Grassetti took third places in Holland and Italy on the 350 and, with a bigger engine, third in the 500cc race at Monza, behind the MVs of Mike Hailwood and Remo Venturi. Venturi became Bianchi’s main rider in 1963, when Tonti increased the stroke to 59mm and created 422cc, 440cc and 454cc versions. In home internationals, Venturi beat John Hartle’s Gilera four in the Imola Gold Cup 350cc race and saw off the MVs of Grassetti and Alan Shepherd in a 500cc race on the Riccione seaside circuit. In 350cc GPs Venturi took second place behind Jim Redman’s Honda, ahead of Phil Read’s Gilera in West Germany, and was third behind Redman and Shepherd (MZ) in Italy. Concerned about costs, the factory reduced its backing for racing in 1964, but Venturi kept the team alive, clinching the Italian national championship. At the early-season Modena international, he collected a 500cc win after Hailwood fell off while leading and was second to Mike at the Cesenatico street race. At Imola he narrowly lost a 500cc race in a ding-dong with Argentinian Benedicto Caldarella’s Gilera. An outing in the Dutch TT saw Venturi take another second, to Hailwood in the 500cc race, and a third behind Redman and Hailwood in the 350. By the end of 1964, the biggest twin had grown by increments to reach 498cc, but Bianchi shut down its racing department at the end of the season. In 1967, the Piaggio Group bought the company and road bike production ended. Tonti began his 500cc Linto project and worked for Moto Guzzi. The engine shown here is a 498cc type, a linear development from the original 250cc twin. Its design shows how Lino Tonti attended to intricate detail to extract high revs and every ounce of power from a vertical twin. Claimed output was 72bhp at 10,500rpm. While the engine’s weight (56kg), width and height are reasonable for a 500cc unit, the earlier 250cc and 350cc versions were bulky for their capacity. Unusually, camshaft drive is not directly off the crankshaft, but via a countershaft behind it. Elaborately-cast crankcase halves join along the engine’s vertical centre line. Containing the transmission as well as the crankshaft and countershaft, they have upward extensions on either side of the main joint behind the cylinders to house the lower part of the camshaft- drive gear train. The crankshaft runs in four main bearings. The outers are 13-roller units shrunk into the crankcase walls, each retained by a plate with four countersunk screws. The inner bearings – a roller on the left and ballrace on the right – are held in a substantial alloy housing which extends back to support the countershaft in a large seven-ball bearing. The crankpins are in 360° configuration, fixed in pairs of full- circle flywheels, beautifully scalloped on their circumferences near the crankpins to achieve balance. Each flywheel has a mainshaft integral with it, and at the centre, the shaft on the inner left wheel press-fits over the smaller one on the right wheel. The sleeve shaft has journals for the inner mains and between them gear teeth cut on the shaft transmit drive to a larger gear on the countershaft. A slot cut in the central bearing housing allows the two gears to mesh. The countershaft gear engages with the lower of two equallysized camshaft drive gears, which turn freely on spindles fixed in the crankcase’s upward extension. The upper of the two drives a third at the rear of a gear case forming the central portion of the vertically-split cambox – alloy in this case, but also made in magnesium. It is riveted to a slim gear locked to the inlet cams on tapers. Two intermediate gears in the casing take drive forward to another cam gear on the exhaust side. If Tonti’s plan for desmodromic valves had come to fruition, the intermediate gears would have been replaced by gears operating valve-closing cams. Each cylinder has its own short camshaft, with an oil-flinger tab adjacent to the cam lobe. The shafts and their driving gears are held together by through-bolts, with needle rollers supporting the shafts’ outer ends. The separate cylinder heads have generous flat-sided finning. Each is held down by four studs, which pass through the vertical iron- lined alloy barrels to thread into the crankcase. The valves are opened when the cam lobes bear on T-shaped pushers with hard shims on their upper faces. They are closed by two-piece hairpin springs with their upper loops retained in saddle plates held to the valve stems by collets. Tonti’s collets engage with two grooves on the valve stems, rather than one. The spring wires’ lower ends insert into blocks surrounding the tops of the valve guides, screwed to the head with socket-head bolts. The guide material is Beryllium copper alloy, once favoured for use in F1 car engines for hardness combined with efficient heat transfer. Hard valve seats are shrunk-in: on earlier engines the valves seated on the head alloy, pre-hardened by hammering. Clearances can be checked through threaded inspection caps on the cambox. Using two 10mm spark plugs in each hemispherical combustion chamber helped produce power without the need for a squish band. The inner plugs, reached through apertures in the cambox, are set at 12° off the vertical while the outers are more angled at 36°. The included angle between pairs of valves is 78°, with the inlets set slightly steeper than the exhausts. Tonti designed special carburettors with integral floatbowls, made by Dell’Orto. Unusually, they have elliptical chokes with a maximum height of 32mm and width of 40mm, approximating to a conventional 34mm size. Flexible hoses connect them to the head via alloy adapters leading to elliptical inlet tracts. Domed crowns on the three-ring pistons have cutaways to clear the valves. Liberally ribbed for strength, the connecting rods have crowded rollers running directly in their big-end eyes and plain phosphor-bronze bushes in the small-ends. Located in the lower crankcase, the oil pump has a vertical shaft, driven off the countershaft by skew gears. Inside the pump are two sets of gears, a lower set to supply the bottom-end and the upper for the valve gear. Oil is drawn up a suction tube from a triple-element gauze filter in the base of the self-contained sump, a finned alloy container held to bottom of the crankcase by eight long studs. The lower gears pump oil through crankcase drillings to feed the crankshaft from both sides, via jets in the ends of the shaft. While feed is direct on the left side, it goes via an external oil carrier on the right. Eccentric cavities inside the crank fling sludge away from the big-end feeds under centrifugal force. Oil flung off the crankshaft lubricates the gearbox. The pump’s upper gears send oil through an external hose that branches into four to feed banjo unions at the outer ends of the camshafts. It passes through the hollow shafts to exit on the cam flanks, draining back to the sump down the camshaft drive column. The countershaft, supported at each end by ballraces in the crankcase walls, extends through the right-side wall to drive an ignition unit. Here, original Dansi kit has been replaced by a Kawasaki CDI system for reliable starting. On the left, a gear held to splines on the shaft by a nut transmits primary drive to the dry clutch. The driven gear has a boss that extends through a detachable oil-tight cover plate to carry the clutch’s lightweight alloy outer basket on splines. Two large needle rollers, side-by- side, allow the gear to turn freely on the gearbox mainshaft. Operated by a pushrod running through the mainshaft, the clutch has six springs retained by bolts in cups on an alloy pressure plate pressing on four plain and four friction plates. The clutch centre hub is also light alloy. The six-speed gearbox is an indirect type with input and output on the mainshaft. The internals are in cassette form with the mainshaft, layshaft, change drum, three selector forks and their spindle, mounted to an alloy bearing carrier plate. The output sprocket is on the right, fixed by splines and a nut to a sleeve gear supported by a roller bearing. The other end of the shaft runs in a ballrace, while the layshaft is in rollers on the left and balls on the right. A detachable housing to the rear of the sprocket contains détente gearchange plungers and behind it a rack engaging with teeth on the end of the selector drum has two pawls and a ratchet inside it to provide a positive stop. SPECIFICATIONS 1964 500CC BIANCHI ENGINE/TRANSMISSION Type air-cooled dohc parallel twin Capacity 498cc Bore x stroke 73 x 59.5mm Compression ratio 9.8: 1 Valve sizes inlet 42mm, exhaust 37mm Valve angle 78° Valve timing Inlet opens 61° BTDC, closes 82° ABDC Exhaust opens 81 BBDC, closes 52 ATDC Valve clearances inlet 0.06in, exhaust 0.08in Carburation 2 x 34mm Dell’Orto SS1 Power output 72bhp @ 10,800rpmWeight 123lbs (55.75kg) Thanks to Martyn Simpkins