BIKES that carry the accolade " factory " have a ferocious reputation to live up to. Any rider hot enough to handle the pace in national or world championships demands a gut wrenching power hit and suspension that’ll land you safely from leaps over tall buildings.
Not entirely true, actually, as motorcyclenews.com discovered when the UK-based Motorex Husqvarna team allowed us the rare treat of a double-header factory bike test on Stephen Sword’s 125 and Carl Nunn’s 250.
So let’s get out on the track and see how much of it’s true about Grand Prix thoroughbreds being barely-tamed wild animals…
Stephen Sword’s 125
Already known in world-class circles for having the power to out drag anyone off the start, Stephen Sword’s bike has a reputation to fear – and one to live up to.
Taking to the track on a bike with a name for itself is a rare experience, so the first few laps are cautious – just to get to know its character.
With the learning laps completed we’re soon howling along Elsworth Moto Park’s wide-open straights like nothing else matters. The taller first and second gears of Stephen’s bike give the engine much longer legs – and particularly the versatile length of second gear, used with the motor’s high revving character gives the engine a remarkably long pull.
First gear is also worthy of note. Riding through tight S-shaped corner sections on any 125 needs careful attention as you try to maintain a fast flowing corner to corner speed. Melting the engine in first gear, or melting the clutch in second gear never quite delivers the kind of traction and drive that’s ideal. The factory 125 Husqvarna takes care of this by using a taller first gear which fills the gap between first and second, allowing the use of first to much greater effect – not to mention off the start gate.
You’ll have probably gathered by now that Stephen’s bike loves to be ridden hard – in fact it demands to be. Pussyfoot around with anything less than a fistful of throttle and you’ll be depriving yourself of the firework show that the motor’s more than capable of igniting. Short shifting is not an option although, like all engines, the meat of the power has to lurk somewhere on the power curve. The 125 Husky’s power sits right at the two thirds point of the rev scale and it’ll sing out loud and strong until you’ve reached near maximum revs before it falls away – just wait for that to happen. Hook another gear and hold it to around 90% and you’ll be spitting dirt at the opposition. Revving any engine to 100% rpm usually causes a falling off in power delivery, and although it’s possible to induce this on Stephen’s bike, you’ll rarely need to go near. Ride the bike in the upper 65%-90% rpm, and it’ll reward you with both a fast lap, and an exhilarating ride.
More good news is that this bike handles with flawless behaviour. Time after time on the dry Elsworth circuit, as the tyres scuffled for grip under heavy breaking, the rear would leisurely drift out whilst skipping effortlessly from bump to bump – trajectory and destination in perfect control.
To describe the suspension in a word, you have to say, soft. But its softness progressively and efficiently firms up proportionate to the amount of compression – unlike a production bike, which more often than not will compress relatively easily up to a " lump " at around the mid point of compression. The lump is where the standard suspension’s progressive damping comes into effect – and it’s usually a case of too much, too soon producing a harsh and sudden resistance, generally disproportionate to the force applied.
The Husqvarna’s factory Sachs rear shock and Marzocchi forks have a hand crafted quality feel to them, offering a continual fluid like motion of near perfect compression and recoil.
Soft is not a word you’d associate with a factory motocross bike, and it’s certainly not a criticism, it’s a compliment. And just for the record, Stephen won his first British Championship race in 2001 by 39.56 seconds, with this soft suspension.
What speeds up must slow down, so it’ll come as no surprise that the Husky’s brakes can stop the action as quickly as they started it. The rear brake lacked a little feel on the dry circuit causing the back end to lock and slide, but on many occasions the sideways glide created a perfect entry angle to the corners and helped to maintain entry speed without the need to force the bike to turn. Strange to get used to because you half expect the frame to object. It doesn’t, so it’s a deadly weapon if used to your advantage.
What makes the factory 125 different from stock?
Starting at the front, the 125 uses production wheels and hubs with double butted spokes and aluminium nipples for added strength. The factory 45mm dual cartridge Marzocchi forks feature low friction Teflon bushes with NOK seals and all internals are finished to the highest possible standards. External fork sliders are coated with carbon nitride and the fork stanchions also feature a hard anodised coating.
The bike’s triple clamps are factory type made by Marzocchi to help stiffen the front end a little although as a rule Stephen prefers the production Marzocchi version. Handlebars clamps are made by 2C.
The 125’s radiators are the standard version and the cylinder and head are factory items which include production porting together with low friction coatings for added performance and reliability. The piston is a standard item, although the team do have an option of a single ringed flat-top equivalent. Stephen’s bike also uses a production crank and water pump.
The power valve is a standard part, but the exhaust is a 2C aftermarket product. The offset bore carburettor also improves the flow ratio into the engine via a V-Force reed block.
The swinging arm and linkage on the bike are production units coupled to a factory Sachs shock which features an increased internal volume to hold more oil, gas and a larger piston.
Frame geometry for the bike is based on the production specifications but strengthened to take the extra knocks and stresses of GP racing.
The airbox is a production unit and the seat is reshaped to suit Stephen. Footpegs are larger and made of titanium to save weight and Stephen chooses to use standard disc brakes with factory brake pads. Brembo brake master cylinders are standard with the addition of an alternative pull ratio on the lever.
Crankcases are made of magnesium and all nuts and bolts are titanium. The silencer is, as you’d expect, made from carbon fibre. The clutch and clutch basket are production units with some slight internal changes to improve the feel.
First and second gears in the 125 are roughly 15% taller than the production equivalent, offering a longer pull on the fast GP circuits, and of course are both very effective off the start gate.
Carl Nunn’s 250
The reassuring news is that virtually everything about the handling, brakes and suspension of Stephen’s bike also applies to Carl’s.
A 250cc engine is heavier than 125s and as you’d expect, the suspension is dialled in to compensate. It’s also important to consider that the larger engine’s power delivery creates a different loading (mostly to the rear end) than the 125.
Once again though the Motorex Husqvarna team have a formula that works extremely well. Overall we’d say that Carl’s 250 felt around 20% firmer than Stephen’s 125 – which also takes into account the additional stiffening for added weight and power. Again though, the 250 displayed immaculate behaviour on the track, taking smaller braking bumps, and larger knocks equally in its stride. Landing off Elsworth’s infamous sky launching jump was an experience and a half on Carl’s bike, and although we managed to bottom the forks on both bikes with regular ease, Carl’s firmer set up helped save our tiring wrists a little more. We have to bear in mind though that the bikes were still set up for the circuit they’d most recently been raced on – Wakes Colne – which is a very different type of track to supercross-style Elsworth.
The power delivery of Carl’s bike is its most unexpected surprise. When we rode Paul Cooper’s original factory 250 Husqvarna in ’99; we got off it thinking we were getting too old for this bike testing lark. Paul’s bike shrieked its way around Elsworth, kicking like an insane stallion, incensed that anyone would dare to straddle its back. Carl’s bike on the other hand has had a long session with The Horse Whisperer and has come out of it enlightened and mellowed.
Hang on a minute. Stephen’s bike has " soft " suspension, and Carl’s bike has a mellow power delivery? Surely not?
Well, it’s true. Nunn’s factory stallion is a mild mannered machine to ride. The 250cc powerplant produces a mid range flow of usable power which hooks up well, finding traction even on the loosest of surfaces. Bottom end pull is ample, but not outstanding, and top end over rev is on hand but not exceptional.
As you may expect from an ex-125cc racer, Carl has the bike set up to nurture the rider and deliver horsepower to the rear wheel with control and restraint. The result is a mild power release that encourages you to push harder without the risk of the highsiding backlash often associated with world beating two-strokes. Using an engine without a ferocious hit of power keeps rider fatigue to a minimum.
Four stroke power delivery is raved about because its torquey, smooth and easy to ride – so is the factory 250 Motorex Husqvarna.
What makes the factory 250 different from stock?
As with the 125, the 250 uses production wheels and hubs with double butted spokes and aluminium nipples. Motorex Husqvarna have a full option on disc brake selection for the 250 – size, material, holes or solid, all of which are larger then the production version.
The factory 45mm dual cartridge Marzocchi forks feature low friction Teflon bushes with NOK seals and all internals are finished to the highest possible standards. External fork sliders are coated with carbon nitride and the fork stations also feature a hard anodised coating.
Triple clamps on Carl’s 250 are factory type made by Marzocchi to help stiffen the front end and offer a 26.7° steering head angle for quicker turning. Handlebars clamps are Husqvarna’s enduro type which position the handlebars 3mm higher, and 8mm further forward. The frame is made to production geometry from light weight chromoly and reinforced in the high stress areas and includes an aluminium bash plate and titanium footpegs. The sub frame is 8mm lower and 10mm narrower than the production bike with a quick release carbon fibre seat.
The ignition is a factory type 3d, digitally mapped to Husqvarna’s own program. Factory radiators have one extra vane for increased cooling. The fuel tank is standard; feeding fuel to the offset bore TMX carburettor and V-Force reed block.
The refined cassette gearbox features taller first and second gears for longer pull. The clutch is reworked on Carl’s bike to provide a much lighter feel, similar to a 125’s.
The rear shock once again features the full factory 50mm Sachs unit, and the swinging arm has added inner stations for extra strength, coupled to a production ratio linkage.
The engine features a factory barrel and head, together with a lightweight piston and pin and high inertia crankshaft with magnesium inserts. The exhaust system features a 2C main pipe and production silencer, reworked with a slightly larger core.
Brakes on the bike use beryllium calipers for increased heat dissipation with an option of various brake pad compounds.