Husqvarna is a hallowed name in motorcycling whose first two-wheeler was built in Sweden in 1903 but only after the Second World War did it become famous for extraordinarily robust off-road bikes that won many enduro and motorcross titles.
In 1986 the motorcycle division of the company was sold to the energetic Castiglione brothers of Varese in Italy, founders of the Cagiva dynasty, and it's now part of the MV Agusta group.
Now Husqvarnas are built at Cassinetta in Northern Italy; they are still nearly all single-cylinder off-road bikes - with a couple of interesting exceptions, of which this is one.
The SM610S Supermotard was derived from the 1996 TE610E enduro bike, the first Husky to have an electric foot - with a kick-start as back-up. The SM, however, was set up strictly for street riding, its geometry based on bikes used for that insane form of racing.
Which means it is enormously responsive, unbelievably quick-steering and prone to pulling spectacular wheelies with little or no provocation; in short, a hooligan tool.
Guilty on all counts, m'lud.
The SM610S has a very compact, water-cooled, SOHC, four-valve single; despite its name its 98 x 76.4mm bore and stroke give it an actual displacement of 576cc (not uncommon among off-road machines where anything bigger than 450cc is simply lumped together as "open class").
There's a balance shaft but the rev-happy motor is vibratious; there's no flywheel to speak of and the revs rise and fall too fast for the little triangular rev-counter to keep up.
It's fed by a 40mm Dell'Orto carburettor that's been set up to run lean at about one-third throttle - which is where they test for emissions control, Cyril - with the result that it stumbles badly on steady running and pops and spits bad-temperedly through its twin tailpipes on overrun. If ever a machine could be said to have an attitude, this is it.
Above half throttle, however, the thing pulls like a runaway horse, yanking the front wheel off the ground in every gear except sixth (top) and threatening to flip all the way over in first and second. I soon learned to short-shift into second when pulling away and never gave it full throttle until I was in third.
Even so the SM610 went up to 100km/h in the space of one city block without even getting into its power band. It's at its most rambunctious above 5000rpm - but you'd better reserve that for when you have lots of space to play with.
Full throttle
It will tolerate full throttle at 2500rpm, power-thudding a little, and produces strong, even power from 4000 to 7700rpm - as long as you keep the power wound on. The more you twist its tail the more this engine likes it.
(Claimed) power output is a class-leading 41.8kW (I have no reason to doubt that) at around 7500rpm - depending on which page of the company website you're on reading. That translates to outstanding performance for a single, especially on a motorcycle with a dry weight of only 140kg
The average of our four top-speed runs - two in each direction - with the SM610S was 175.8km/h, although it reached a frenetic 192km/h at 8000rpm on one run with a stiff South-Easteraster helping. Nevertheless, don't expect it to pull more than 7300 revs in still air - which is still good going for a short-geared city bike.
The engine is distinctly cold-blooded so refuses to start - hot or cold - without full choke and stalls very easily pulling away when cold, which lends credence to my lean-running theory.
It's mechanically noisy but that's mostly masked by thudding intake roar and a harsh, flat, only-just-legal bark from the twin stainless-steel end cans tucked up under the saddle.
The tiny wet clutch - it's inside the gold-anodised cover on the right of the gearbox - is a little grabby, especially when it's cold, but seems bulletproof like most off-road clutches; they have to be, because they take a lot of abuse.
The gearbox is a honey, slick and quick-shifting; typically Italian, it's a little clunky from first to second and occasionally reluctant to find neutral but crisp as fresh lettuce on the move.
Within 100m of picking up the test bike, seamless upshifts were the order of the day - and we didn't miss a shift during the test period.
Uncomplicated chassis
This engine is mounted in an uncomplicated tubular steel chassis, with top-quality suspension components. The 45mm leading-axle Marzocchi forks are adjustable for compression and rebound damping while the Sachs piggyback monoshock is tunable for low and high-speed damping and preload.
The chassis shows the normal Italian failing of painstaking attention to detail in some areas while overlooking simple things in others; the suspension has been revalved to suit the bike's intended role as an urban terrorist and made it the best-handling machine in its class - but none of its ergonomics has been revised.
The SM610S has a plank-like enduro seat and vibration-prone cleated footpegs so it's uncomfortable on a long rides - I found myself standing on the pegs at 120 on the freeway on the way home to give my backside a rest.
The stainless-steel spokes and 17" alloy rims are superb, as is the racing-standard four-pot Brembo front brake calliper - but the original dinky little master cylinder is still in place. It has too little volume to push enough brake fluid to operate the heavy-duty calliper, so the front brake lacks power and feedback.
It works - but it would work a lot better with a bigger master cylinder such as the standard Brembo unit off any Ducati Monster; there should be plenty of those in breakers' yards.
The rear brake is much smaller, very similar to the original item on the TE610E, so it works fine with the existing master cylinder.
Superb handling
The SM610's handling is utterly superb; at low speed it turns in frighteningly quickly, but the front wheel never tucks in no matter how hard you load it - although it sometimes feels like it's going to - and the more you ride this bike the more confidence you have in its ability.
Give it big handfuls of throttle and it goes through the traffic like a squirrel, in short, frenetic bursts - you have to concentrate all the time but you arrive at work feeling so alive it's a shame to sit down in front of a computer.
Employers beware - the Husqvarna SM610S can contribute to absenteeism and delinquency among employees.
And yet out on the open road the Husky holds its line fine; the damping is much stiffer than you'd expect on an off-road machine with long-travel suspension but it pays off - this is the only supermotard I've ridden that doesn't shake its head going flat out in a straight line.
Soft brakes and all, this thing will out-corner most sports bikes on the way in and out-punch them coming out - it's only at top end that the race replicas will come steaming by and on tight back-country roads.
But that's not what this bike was built for - it's an outright street machine with lots of street cred.
Patchy detail work
The detail work is patchy; the switchgear is standard stuff, as made by CEV for countless Hondas, and the small, square headlight throws a strong evenly-spread beam with a sharp cut-off - but there's no backlighting on the small, custom-made instrument pod so you can't read the clocks at night and you have to ride by ear.
The black plastic body panels are thick, tough and very neatly moulded - but in true enduro fashion the stick-on graphics are shoddy and have no clearcoat to seal them in place.
It's almost as if you're expected to change the bike's graphics for every season.
And that about sums up Husqvarna's street-smart supermotard; it's rambunctious, vibratious and so in-your-face that you find yourself shouting back at it.
I'm still young enough to love its hard-rocking, full-tilt persona but old enough to know that I couldn't live with it in the long term.
Thanks to Husqvarna rider Donovan Rodgers, who loaned us his own bike for this review; the SM610S costs R69 000.