Photos: Kyoichi Nakamura
JJ-Cobas-BMW K 100 R
Four-cylinder racer from BMW
In 2009 BMW wants to enter the Superbike World Championship. Bayern have already won a Spanish championship? 24 years ago. Carlos Cardus won 1984 on a JJ-Cobas-BMW K 100 R. MOTORRAD employee Alan Cathcart drove the oldie.
What has not happened in the last two decades. Not only in motorcycle development, but also here. I notice that from the first few meters with the JJ-Cobas BMW ?? named after its Spanish builder Jacinto "YY" Moriana and Antonio Cobas ??, who bring back memories of a time long believed to be forgotten.
The sitting position, for example, is stretched out with the upper body bent forward to transfer weight to the front wheel. Especially when cornering, arms and shoulders have to bear the weight of the upper body, which otherwise rests on the 24-liter tank. That’s how it was back then when the engineers were still looking for the best compromise between handling, stability, grip and weight distribution.
To some extent, her recipe still works today. For example in the chicane on the Mallory Park course east of Birmingham: I have never driven another motorcycle there that is so easy to control. For a bike with such a concept and weight (179 kilograms), the JJ-Cobas-BMW feels agile. Even in the fast corners like Gerard and Esses. There you can feel how the DeCarbon shock absorber works and iron out small bumps. The good surface makes it possible to take advantage of the adhesive power of the 16-inch rubbers and to drive with great inclination and considerable speed. Thanks to the low center of gravity, the BMW can be set up again quickly or turned over on the other side. The stability on the straight is hardly surprising in view of the chassis data, wheelbase tight 1440 millimeters, steering head angle flat 62.5 degrees.
Brakes and smoothness
It’s amazing how agile the JJ-Cobas-K 100 R can be.
That 1984 was a long time ago is particularly evident on the brakes. The two 300-millimeter discs slow down to an acceptable level, and thanks to the hydraulic AntiDives, the fork does not dip too deeply. However, in order to then initiate the curve, you need a lot of force on the handlebars. And in an inclined position, you have to hold against it permanently so that the BMW does not straighten up. A typical reaction from bikes of the 1980s, especially when they rolled on 16-inch tires. If you brake into a curve, you run the risk of missing the apex. I only manage to create a rounded line when I move the Cobas BMW according to its age. So: complete the braking process before the bend, only then bend and pull the gas evenly from the apex of the bend.
That costs valuable tenths, but it works well because the four-cylinder in-line develops its power linearly. Sufficient power is available from 4000 tours and this lasts up to 9400 tours without a drop in the torque curve. The peak output of 124 hp is there. For comparison: today’s superbikes have almost 220 hp. After all, the JJ-Cobas-K 100 R brings 33 hp more than the street version. And the engineers have achieved this plus in performance solely with classic tuning measures such as larger ducts, sharper valve timing and more valve lift, higher compression. What is decisive, however, is that they use the standard, electronically controlled fuel injection ?? the JJ-Cobas-BMW was the world’s first superbike with EFI ?? have retained. It offers better tuning options than carburettors. The mixture regulation does not take place via the programming, but mechanically via an adjusting screw.
A sixth gear is missing on the long straights, so you have to hold back. A slip clutch, as it has become a matter of course, wouldn’t be bad either. Anyone who shifts from second to first without using the clutch generates violent reactions from the cardan drive and a thud in the transmission. One more reason to use the elasticity of the engine and avoid first gear. It is only inevitable before the sharp hairpin bend. The high drag torque of the four-cylinder makes the rear wheel bounce. That is why it is better to disengage the clutch before tight bends and accelerate out like when starting the traffic light. The first gear is longer than the second in the production version, but still too short ?? at least by today’s standards. But even they show that the JJ-Cobas-BMW K 100 R was way ahead of its time back then.
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