|
BMW R 90S
|
Make Model |
BMW R 90S |
|
Year |
1974 Number Sold 17465 |
|
Engine |
Air cooled, four stroke,
two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder. |
|
Capacity |
898 |
|
Bore x Stroke |
90 x 70.6 mm |
|
Compression Ratio |
9.5:1 |
|
Induction |
2 slide Dell'Orto PHM 38 carb |
|
Ignition /
Starting |
Battery ignition /
electric |
|
Clutch |
Dry single plate,
with diaphragm spring |
|
Max Power |
67 hp 48.8 kW @ 7000 rpm |
|
Max Torque |
76 Nm 55 ft-lb 7.6 kg-m @
5500 rpm |
|
Transmission /
Drive |
4 Speed /
shaft |
|
Gear Ratios |
4.4 / 2.86 /
2.07 / 1.67 / 1.50 :1 |
|
Frame |
Double-loop tubular frame
with bolt-on rear section |
|
Front Suspension |
Telescopic hydraulic forks. 208mm wheel
travel |
|
Rear Suspension |
Long swinging arm with adjustable strut.
125mm wheel travel |
|
Front Brakes |
2x 260mm disc 1 piston caliper |
|
Rear Brakes |
200mm drum |
|
Front Tyre |
3.25 H19 |
|
Rear Tyre |
4.00 H18 |
|
Seat Height |
820 mm |
|
Wet-Weight |
215 kg |
|
Fuel Capacity |
24 Litres |
|
Consumption average |
46
mp/g |
|
Standing
¼ Mile |
13.3 sec /
101 mp/h |
|
Top Speed |
200 km/h |
|
Reviews |
Beemergarage.com
-
Test 2 -
Test 3 -
Test 4 /
Motorcycle-USA
/
Top Speed |
|
Manual |
5united.net |
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 I25mph (2()lkm/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 fiat 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 gearchange 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
7()00rpni. 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.
Comfortable ride
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 from when approaching its lop speed, but That was even more
true of most naked rivals. The twin-disc from 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 seal that allowed
the rider lo 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. Thai 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 lo 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 (he quickest superbike round a racetrack, too. BMW ace Reg
Pridmore's victory in the 1976 US Superbike championship was proof of that.
Source Fast Bikes by Roland Brown
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