Yamaha XS750
The Yamaha handled well despite being a fairly heavy bike with shaft final drive.
The original XS750’s rounded styling, silver paintwork and black- finished three-cylinder engine gave a distinctive look from the front.
Few bikes have arrived to such a warm welcome as Yamaha’s first big four-stroke superbike, the XS750 triple, whose performance, distinctive style and versatility made it highly rated by press and public alike on its launch in 1977. And fewer still have followed that initial impact by fading from the scene quite so quickly, having failed to make a mark on a superbike market that was suddenly awash with high-quality alternatives.
On paper, the Yamaha looked a winner to its last, carefully considered detail. The basics were very much in place. Its engine was a 747cc aircooled triple with twin overhead camshafts, a 120- degree crankshaft (for smooth running) and shaft final drive. Yamaha’s designers had kept the engine compact by using bevel gears to turn the crankshaft’s drive through 90 degrees for the drive shaft. With a maximum output of 64bhp at 7200rpm and plenty of mid-range torque, the triple came very close to matching its sportier chain- driven four-cylinder rivals for pure power.
This unique engine was matched to rounded, distinctive styling and a relatively conventional but cleverly designed chassis. The twin-downtube steel frame employed substantial bracing around the steering head, in the fashion of the BMW’s R75 twin. Forks and twin rear shocks were typical Japanese items. The Yamaha was rather tall and it was heavy at 5141b (233kg) dry. But it was also well appointed, with a roomy riding position, clear instruments and self-cancelling indicators.
Straight-line performance was undeniably impressive. The Yamaha’s motor was smooth, tractable and powerful, sending the bike to a top speed of 120mph (193km/h) and allowing effortless high-speed cruising. Its three-cylinder layout gave a pleasant character, with the bonus of a distinctive exhaust note. And the XS had an efficient five- speed gearbox as well as its shaft final drive system, itself a real benefit in the days of fast- wearing drive chains.
That drive shaft had almost no adverse effect on the Yamaha’s handling, which received much praise although the bike was designed for comfort as much as for agility. ‘We failed to make it waggle, weave or twitch and we tried our damnedest,’ enthused Bike magazine’s experienced tester, who summed up the XS750 as the best Japanese bike and best all-round touring machine he’d ever ridden - including numerous more expensive BMWs.
Comfortable cruising
Long-distance comfort was good by the standards of unfaired bikes, thanks partly to the generously padded dual-seat. One criticism was that the fuel tank was too small for touring, but this and the poor headlamp were the only criticisms, apart from the mediocre wet-weather performance of both tyres and disc brakes, which was typical at the time. Given the Yamaha’s very competitive price, it looked set to become a big hit.
But the motorcycling public decreed otherwise, partly because of the rival attraction of fours including Honda’s proven CB750, Suzuki’s new GS750 and Kawasaki's cheaper Z650; and partly because the Yamaha quickly earned a reputation for unreliability. Troubles included piston ring failure, seizure of the central cylinder, rapidly wearing primary drive chain and ignition points, plus the gearbox’s occasional trick of jumping from fourth straight into first.
Word of the unreliability spread, and the XS750 never recovered. Yamaha made a series of updates to cure the problems, and in 1978 improved the triple with the XS750E model, which had an extra 4bhp, revised lubrication system and uprated front suspension. But the damage had been done, and neither that model nor the revamped XS850 that followed two years later could bring Yamaha’s triple the success that had once seemed so assured.
Chassis layout was typical of the mid-1970s, with twin-downtube steel frame, non-adjustahle telescopic forks and twinrear shocks. Compliant suspension and the broad dual seat helped make the Yamaha a useful longdistance machine, despite its small fuel tank.
Yamaha’s 747cc twin- cam triple initially impressed all who rode the bike with its 64bhp output, smoothness, abundance of mid-range torque, and unobtrusive shaft final drive system. But the Japanese firm's insufficient development testing of its first big four-stroke engine became clear from the XS750's inherent mechanical problems.
Specification Yamaha XS750 (1977)
- Engine Air-cooled dohc six-valve transverse triple
- Capacity 747cc (68 x 68.6mm)
- Maximum power 64bhp @ 7200rpm
- Transmission Five-speed, shaft final drive
- Frame Steel twin downtube
- Suspension Telescopic front; twin shocks rear
- Brakes Disc front and rear
- Weight 5141b (233kg)
- Top speed 120mph (193km/h)
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