Motocross

Stefan’s stable

Stefan’s stable

NO MATTER from which angle you look at Stefan’s #72 YZ450FM it’s beautiful. Absolutely beautiful. NO MATTER from which angle you look at Stefan’s #72 YZ450FM it’s beautiful. Absolutely beautiful. With its distinctive blue and red L&M livery, striking black-painted frame and black wheels, the bike looks every bit the world championship winning machine it is.
But strip away all the brightly coloured plastics and carbon fibre guards and you have a machine that’s 10 times closer to a production bike than either of Stefan’s 500cc championship-winning bikes from ’01 and ’02. With no special aluminium chassis or increased engine capacity, it’s clear that fine-tuning – and not serious performance enhancements – is where the team’s energies have been focused this year.
But you wouldn’t expect Stefan Everts to have won the ’03 MXGP title on a stock bike – and he didn’t. While the bike’s architecture is very similar to a production YZ450F – some of it is, in fact, identical – the bike does feature numerous changes and several special parts. Not least the factory Kayaba suspension and Brembo brakes.
If Yamaha’s motocross press kit is to be believed, the ’04 YZ450F has been both an easy and difficult bike to prepare for MXGP competition. Easy because according to team manager Michele Rinaldi the production bike, on which the YZ450FM is based, already has a "very well balanced engine and chassis". And difficult because it was therefore "not easy to raise the competitive level of the machine that much further".
To be competitive at GPs means that ultimate performance must be the goal so the Rinaldi technicians have worked hard to produce a bike capable of performing at the very highest level of the sport. To do this the focus was not put so much on serious performance gains but on fine-tuning the engine to suit the needs of the team’s riders. As a result the number of special parts is relatively modest for an official factory machine.
But those special parts replace many of the engine’s major components. Piston, con-rod, cylinder and crankshaft are all ‘special’ YRRD (that’s Yamaha Rinaldi Research and Development) parts, helping the engine produce a power curve that shows increased performance over the entire rev range. Something that’s also in part achieved by fine-tuning the cylinderhead and carburettor. With YRRD ignition that features unique mapping, giving an even smoother feeling engine, the team also do ‘a little work to the cylinderhead’ and use different cams.
In fact, they have many different cam possibilities – it just depends how their rider likes his motor to feel. Compared to the standard YZ450F cam, the ones fitted into Stefan’s bike help the motor produce a stronger mid-range – just the way he likes it. And there’s just that little bit extra top-end oomph as well.
While the engine does feature many changes over standard, one area of the bike that doesn’t is the chassis. Mirroring the production specifications – and in a departure from the aluminium YZ500FM chassis used last year – the team now use a standard YZ450F frame with unaltered geometry.
The only modifications are the bike’s lengthened swingarm for improved stability and better starts – but they wouldn’t tell me exactly how much longer it was – plus a few altered brackets to accept a sumpguard and Brembo rear brake master cylinder and machined triple clamps that modify the offset of the forks. According to the team’s mechanics, they have clamps with varying offsets from 20 to 28mm that are used depending on whether they’re racing in sand or on hardpack.
Two areas of the bike that differ significantly from the standard machine are the brakes and clutch. Replacing the standard cable-operated unit, a hydraulic clutch is fitted for two reasons. Firstly, it’s lighter and with no free play omits the need for adjustment during the race. Secondly, it has a more progressive action.
The brakes, which are developed in close collaboration with the Rinaldi team, are manufactured by Italian company Brembo and feature a beryllium front brake caliper powered by new master cylinders similar to those used on the KTM factory bikes. The team actually only use a Brembo unit on the front of the bike and a ’02 Yamaha caliper on the rear because it’s fitted with a different sized piston to the ’03 unit. The bike’s brake set-up is completed by 270mm and 245mm Braking discs.
The biggest – and one of the most beneficial – changes to the bike is the use of the factory specification KYB suspension package. Featuring 50mm USD forks and a shock that’s based on the production unit but features internal modifications and runs both high and low-speed compression damping systems, the striking thing is just how soft and fast the suspension is.
With very little static sag at the back, by pushing down firmly on the rear of the seat the shock can be made to move down almost into its mid-stroke. Likewise, when released it returns at a rate that almost suggests that the shock’s lost all its nitrogen. But the action of both the forks and shock firm up considerably to deal with the kind of warp-speed hits Stefan inflicts on it.
The remaining changes to the bike are those made to every serious GP machine. Using titanium almost everywhere saves weight and where it isn’t used, nine times out of 10 you’ll find aluminium items. Carbon fibre guards protect the sump and rear chain guide and it’s also used for the engine mounting brackets and wrapped around the fork legs. Aggressive titanium footpegs, Acerbis plastics, Pirelli rubber and Everts’ bend Tommi bars and Pro Grip grips finish the bike. Interestingly, the wheel hubs used on Stefan’s bike are standard with only a special coating.
One thing that you notice about the way in which Stefan’s bike is prepared is the number of areas that are modified as a precautionary measure and not to improve performance. With the footpegs and the steering head nut wired into position, the L&M Yamaha mechanics even run a zip-tie around the bolt that holds the launch device in place, just in case that bolt should fail. Another thing you notice is how everything has an exact place – each cable is routed in a very definite way, each hose follows a very definite path. And wiring looms are attached to the frame in an exact and precise way. Wherever an electrical cable is attached to the chassis, black electrical tape is first run around the frame for two reasons. Firstly, so that the mechanics know exactly where to connect the cable to and secondly because the plastic tape offers slightly more friction so that the cable won’t slip or become loose. It’s those little details that give the bike a true ‘factory’ look.
By his own admission, Stefan likes to have progressive power and a very strong mid-range. The reason? He likes to use just one gear – third – as soon as gets the jump out of the gate. Not because he’s getting old and lazy but because he says it makes his corner exit speed quicker as he doesn’t have to worry about shifting. The seven-time champion also likes to have his levers up high, a seat that isn’t too high – he likes to feel aerodynamic on the bike – and a bike that offers him good traction on the front end because he spends so much time up on the pegs.
When riding the bike it’s clear that whatever Stefan’s asked for from his L&M Yamaha team he’s got – a bike with an incredibly strong mid-range. With a noticeably shorter second gear than standard – something that Stefan admits has helped him get out of the gate so well this year – third gear goes on and on…and on…and on. In fact, third gear linked to the bike’s final drive of 15/50 is the only gear you really need, especially if you’re able to carry massive amounts of corner speed like Stefan. If you’re not – and few riders are – then while third gear will happily pull you around even the tightest of corners, it’s second gear that feels more comfortable. The only problem with using second gear is that you find yourself having to shift as soon as the bike starts to exit a turn – the exact reason Stefan keeps his Yamaha in third.
What’s really impressive – and what makes the bike so much easier to ride than a standard YZ450F – is the fact that the motor’s power comes in with no hit at all. It isn’t in any way aggressive, although it’s immensely strong and has huge amounts of torque which is a great thing as you can just roll the power on and off whenever needed. With so much torque and mid-range grunt the bike enables you to focus solely on choosing lines as you don’t have to think about anything other than braking and accelerating. What is interesting is that the bike produces power similar to an older, dare I say it, ‘Euro-style’ thumper at times and not that of the hard-hitting modern-day Japanese four-stroke. Okay, so it’s one hell of a compact, lightweight and powerful motor but it does feel surprisingly like a four-stroke of old and reassuringly easy to ride. There’s definitely no aggressive, hard-hitting power with Stefan’s bike.
Like the motor, the bike’s suspension’s also surprising. I expected the fact that I was around 15kg heavier than Stefan – basically, too heavy for the bike – to be cancelled out by the fact that he’s so much faster. The suspension I guessed would probably be just about right for me. It wasn’t. It was too soft. The initial part of the stroke on both Stefan’s KYB 50mm USD forks and shock is incredibly soft. When you arrive at the mid-stroke it firms up considerably but progressively – although when braking heavily across bumps entering corners the suspension felt too hard on occasions because it was running mid way into its stroke. On the rest of the track it felt very responsive, giving great feedback from the track. That and the fact the bike felt extremely light made it incredibly easy to manoeuvre. As the mechanic told me afterwards, "it only really works for Stefan".
One thing you notice when riding the bike is the shape of the clutch and front brake lever encourages you to leave one finger on each at all times. Extremely comfortable and offering you the luxury of instant use, I also noticed that Stefan runs his front brake lever very much closer to his hand than most riders. With the Brembo unit offering a very firm and positive action, both brakes – the front especially – were excellent.
So what did I learn from my day in the presence of greatness? Well, firstly that Stefan likes very soft and very fast suspension, a linear motor with exceptional bottom and mid-range power and levers that point towards the heavens. Oh, and that if production 450s produced the smooth useable power that Stefan’s does the average man on the street would enjoy riding them much, much more. With Stefan’s 450 being impeccably prepared and exceptionally well set-up, I also realised that the days of the true full-blown factory GP bike are now a thing of the past. Replacing them are production-based machines that feature only a handful of parts that can’t be bought for love or money.
But more importantly – and as I had already suspected – the monkey and not the machine is the more important half of the rider/bike duo, especially where winning world MX titles are concerned. Don’t get me wrong, Stefan’s MXGP steed is an exceptional piece of machinery and one that I felt was much easier to ride that a standard ’03 YZ450F – it’s just that to extract the best from the YZ450FM you need to be exceptionally skilled and exceptionally fit. After all, if it was the bike that made all the difference why wasn’t I able to glide my way as effortlessly and as quickly around the Asti motocross track as Mr Everts?
Words by Jonty Edmunds