Coupled with a new engine management system labelled BMS-C II, which has upgraded software with a considerably enhanced range of functions, the company claims that the "2 spark" series motor will comply with the Euro 2 emission standards and deliver improved fuel economy and throttle response.

Peak output and torque, it says, remain the same but maximum torque is now produced at 4800rpm instead of 5500.

The result is a big single that runs like a twin; apart from some restrained power-thudding below 4000 revs and unexpectedly buzzy secondary vibes above 5500, the motor is uncannily smooth, giving no hint of the coffee can-sized piston humping up and down below the (dummy) fuel tank.

Throttle calibration is as accurate as a German railway timetable; its response is so instant and the motor's midrange so strong that you can easily be fooled into thinking that there's more than 37kW on tap.

One tends to judge this bike by the standards of bigger, more powerful machines – which is actually a big compliment for the Spandau single. It'll pull, shaking a little, from 1800rpm onwards, where our editor's 1999 F650GS needs at least 3000 on the clock before it stops jerking and settles down.

Between three-five and seven it accelerates hard and fast, the jetting so clean that you can open and close the throttle with only a hint of the dreaded spritzer "slamming door".

After 7000rpm the power curve rapidly falls away; the final gearing is a little shorter than on earlier versions, so the bike gets up to 160km/h very rapidly but you have to hunker down and make yourself small to get the last 12km/h.

The test GS topped out at 172km/h after a long run with the rev-counter way past the power peak at 7250. Longer gearing would give you more top end, but at the expense of the bike's spirited mid-range.

Variable rev limits

The red line on the distinctly more professional-looking instrument panel starts at 7500 but I was amused to note that the new engine management system imposes varying limits in the different gears.

In first the rev limiter cuts in very suddenly at 6400rpm, in second at 6600 and at 7000revs in third and fourth; only in the top two gears will it allow the motor to rev out.

It's a good way to protect the motor from ham-handed riders and wheelie freaks.

The rest of the drive train is unchanged; the clutch is as bullet-proof as ever, while the five-speed gearbox is a little notchy at low revs but slick and quick above 3500rpm – although the first-second change remains noisy.

I think it's a BMW tradition.

After 10 minutes on the bike seamless changes in both directions were standard and I thought no more about the transmission – which is a compliment in itself – until I missed a gearshift (my fault, not the bike's) on the last day of the test.

Through all this hard riding and long fast runs the new GS returned an impressive fuel consumption of 5.35 litres/100km; BMW claims that it'll do 3.2 at a steady 90km/h, which is believable, although it would require a very disciplined right hand! (Interestingly, our ed gets five per hundred from his older bike.)

Improved handling

With 4.7° more rake than the 1999 version the latest GS is infinitely more stable, but thanks to visibly reduced trail, flicks effortlessly from side to side through the editor's favourite S-bends.
That and the ultra-smooth, almost too civilised, motor were the main reasons why he thought the bike an improvement over his own.

The 41mm Showa forks have a built-in brace, which prevents "walking" when you apply the single Brembo front disk brake.

There's significant front-end dive, as on all dual-purpose bikes, but the bike tracks perfectly under hard braking and the long-travel suspension does a superb job of soaking up life's little inequalities.

The rear suspension is adjustable for damping and preload, the latter by means of a remote hand wheel sticking out alongside the cylinder head on the right of the bike – marked in French for some reason.

All day comfort

Together with the wide soft saddle and the relaxed seating position, just forward of upright, they make the F650GS unexpectedly comfortable for a midweight beetle-crusher; it's one of the few bikes which truly deserve the accolade "all day comfort".

I did indeed spend one whole day on it, combining a long fast run with some not very adventurous off-roading and a long, lazy afternoon just drifting around the West Coast at 90km/h. I can't think of another bike which would have done all those with as much aplomb and as little rider fatigue.

The wide bars give plenty of leverage for throwing the bike around, ground clearance is for all intents and purposes unlimited and the quality suspension components keep the bike going exactly where you point it.

Within the limits of its performance envelope (i.e. up to 160km/h) it's a surprisingly competent sports bike that lends itself to flat, track-style overtaking manoeuvres with late braking and early apexing its primary strengths – along with a huge Grin Factor!

GS styling

The body panels have been re-styled to look more like the bigger, boxer-twin GS model, with a long beak-like extension under the headlight as well as a more conventional front mudguard, none of which stops the bike from throwing mud all over itself.

Don't try turning a hose on it as you would a conventional off-road machine – as the bike dries out all the mud is still there. Knuckle down and wash it properly with soap and hot water – the results are worth it.

Don't forget to wash out the inside of the aluminium bash plate as well; I got more than a cupful of sand and mud out of there.

The bigger front headlight has a clear polycarbonate lens and a free-form reflector, giving a huge and very effective spread of light.

The restyled screen, however, does little more than keep the flies off the new, more sharp-edged instrument panel, with its easy to read grey-faced dials and central warning light cluster.

Dakar screen

The Dakar version comes with a taller, more stylish screen which will interchange with the "standard" version. It's available as an aftermarket part in both clear and smoked plastic, giving extra protection out of all proportion to its minimal extra size – don't hit the long road without it.

Note that the only way to clean the screen properly is to remove it, which requires taking out just four bolts, the Torx key for which is in the toolkit.

Both levers are adjustable for even really small hands; together with BMW's optional lowered seat kit, they make the GS an outstanding choice for smaller (read female) riders.

The dummy fuel tank has a new vent panel on either side with a Blue Propeller badge in the middle, strongly reminiscent of the iconic 507 sport car of the 1950s (no accident, I'm sure).

BMW assures us that it's there to direct cooling air in to the body cavity and force hot air down and away from the oil reservoir which occupies most of the space usually taken by the fuel tank.

The cast-alloy rear carrier is now properly integrated into the tailpiece, with slots for tie-downs and the right holes for bolting on BMW's own Givi-style top box without an adaptor plate.

Flimsy cover

BMW says it has beefed up the plastic lid of the little storage compartment in the middle of the carrier, but it's still embarrassingly flimsy. You could pop it open with a screwdriver, giving you access to whatever's stored inside as well as the catch for the seat – which is well worth stealing, considering BMW's spare parts prices.

Next to the rear suspension hand wheel you'll find the power socket for charging the battery, while new jump-start points (the positive connection is under the seat and the negative terminal is on the gearbox cover) enable the rider to jump-start the machine without having to remove any body panels – all of which says more about BMW riders than it does about their machines.

The fourth-generation F650GS is a superb go-anywhere, do-anything bike, flexible enough for commuting, nimble enough to scorch the tar on your favourite passes, sure-footed enough to tackle any jeep track and comfortable enough to make a decent light tourer.

It's available in three colours: plain yellow, black and metallic silver, while the Dakar version with taller suspension and 21" front wheel comes only in metallic blue/pearl white.

BMW, as always, offers a host of add-ons like like top box, panniers, soft panniers and tank bag, hand guards. You can also order your GS with lowered seat, heated grips and ABS.

• Test bike from: Auto Atlantic, Cape Town. Price: R63 950 (heated grips and ABS R5200 extra).