BMW R90

BMW R90

BMW R90 in orange body paint

On pure performance, 

BMW's R90S was not the fastest superbike of the mid- 1970s. Nor was it the quickest around a racetrack; at least, not often. But for a rider with a long distance to travel on straight roads and twisty ones, there was nothing on two wheels that would prove faster or more comfortable than the uniquely well-equipped flat twin.

The BMW's distinctive smoked paint scheme was perfectly in keeping with its image as a very refined and expensive sports-tourer. In many respects, the R90S was the best all-round superbike of its day. Certainly, no other production machine could match its combination of 125mph (201km/h) top speed, relaxed high-speed cruising ability, fine handling, reliability and impeccable finish.

BMW had plenty of practice in building horizontally opposed twins, and it showed. The R90S came from a line of flat twins stretching back to Max Fritz's original R32 of 1923. The German firm had been building competent, comfortable and conservative tourers for many years. But this bike, shaped by noted stylist Hans Muth. had a distinctly more aggressive personality.

The basics were typical BMW. Like the naked R90/6, which was launched at the same time in 1973. the R90S owed much to the previous year's R75. Enlarging the 745cc R75's bore from 82 to 90mm while retaining the 70.6mm stroke increased capacity to 898cc. BMW also made a few other updates, including a revised gear change mechanism, more powerful 280W alternator and stronger bottom end.

There was more to the S-bike than just its fairing. The engine was given a higher compression ratio, 9.5:1 against the 9:1 of the R90/6, and breathed in through big 38mm Dell'Orto carbs with accelerator pumps. Maximum power was 67bhp at 7000rpm, an increase of 7bhp over the standard model. The R90S also had a steering damper in its cockpit, a larger fuel tank and a second front brake disc.

The extra power gave the S model a worthwhile boost at high revs, without hindering either its torquey mid-range response or its smoothness at most engine speeds. Better still, the fairing meant the engine's performance could be fully exploited by the rider, who was free of the wind-blast generated by every rival superbike. Other manufacturers would soon follow BMW's lead, but for the moment the fairing put the R90S in a class of its own.

BMW R90

Comfortable ride

BMW R90

Handling was good, too, despite suspension that was soft enough to give a comfortable ride. Notwithstanding its steering damper the S sometimes felt light at the front when approaching its top speed, but that was even more true of most naked rivals. The twin-disc front brake system was reliable but lacked feel until uprated in 1975. Neat touches included a dashboard clock, generous fuel range of 200 miles (322km) or more, and a seat that allowed the rider to cover that distance in comfort.

BMWs had never been cheap, and the R90S, with its all-inclusive specification, was no exception to this rule. In many markets it was more than twice the price of Honda's CB750. That ensured the R90S would be ridden only by a select band of riders. Although the bike was a success, it was outsold by the standard 90/5.

Those riders fortunate enough to cover serious distance on the R90S knew that it was a very special motorcycle. If what you needed was a speed, handling ability and comfort, the R90S delivered in style. Oh, and sometimes it was the quickest superbike round a racetrack, too. BMW ace Reg Pridmore's victory in the 1976 US Superbike championship was proof of that.

BMW R90  prices 2014

MINT                       $9,000               £7,000

GOOD                      $7,500              £6,000

FAIR                         $5,000              £5,000

PROJECT                $1,500               £1,000