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How Jerry Burgess and Valentino Rossi turned the Yamaha M1 into a winner

— from ‘2004 MotoGP Season Review’ by Julian Ryder

Valentino Rossi won his third MotoGP title in a row in 2004, but this time he did it on a Yamaha, a bike he’d first sat on in January. Moreover, this was a motorcycle that had so far proved comparatively unsuccessful. To take the title in your first year on a new bike is pretty unusual; to do it on one as previously ill-starred as the M1 is a real achievement.

(The complete team. clockwise from back left: Gary Coleman, Alex Briggs, Jerry Burgess, Matteo Flamini, Bernard Aisnau and Brent Stevens)

ROOTS

The Yamaha M1 was initially a very fine-handling, agile, compact four-cylinder Grand Prix bike, but from the start it didn’t have the necessary power. Yamaha’s engineers didn’t even make the engine the full 990cc, believing that the resulting power would be unusable. Once Honda had demonstrated that more power certainly was usable, Yamaha had to play catch up all through 2002. For 2003 Yamaha thought they had the right mix of rider - Barros at the top of his form - and a heavily revised motorcycle that was going to give them the results they craved. All through IRTA testing, at the start of the 2003 season, it looked as it they had indeed arrived. They were upbeat and confident even showing off one of their experimental prototypes, but at the first race at Suzuka Barros was injured and everything fell apart.

Big organisations don't react very well to failures of this magnitude, and Yamaha had several different but pressing issues to deal with. Not only was their now very damaged pride at stake, but 2005 would be their 50th anniversary, -and they wanted to win the MotoGP championship to celebrate It was time to fix the problem once and for all. Every business has its fixers managers who seem to be able to make the previously unworkable work and Yamaha found one in Masao Furusawa. He had served with distinction in several parts of Yamaha's empire and he took control of the newly renamed Technology Development Division in April 2003.

INITIAL DESIGN

Yamaha decided that the in-line four was the best way forward, it's a configuration that, in simple packaging terms, is a very compact power plant. Theres no second bank of cylinders to squeeze in at the back, the engine is wide where there is room for it to be wide (in front of the rider's legs), and with one cam drive, one set of cams and one cylinder block it should be fairly light - it's a full 18kg less than the R1 motor.

The initial chassis was based on the YZA500 two-strokes Shortish and quick turning, this chassis had straight beams and came with a muiti-adjustable engine position. By the second year the chassis was more settled. A new arched Deltabox design put the engine into a position that worked well enough not to need major adjustment.

The engine developed in the same way: Yamaha's initial assumption that the full power of a racing 990cc four couldn't be used in a motorcycle proved sadly wide of the mark. The first bikes were below the full capacity to try and match power and torque with available grip. For 2003 the engine was a full 990cc.

It seems incredible now but, in its first year, the M1 had carburettors: the fuel-injection system only arrived on Barros's bike in 2003 pre-season testing. When the press rode the bikes at the end of 2003 their main observation was how peaky they were, although in a speed-gun test at the same time the Yamaha showed very similar acceleration to the Honda. The problem wasn’t the amount of power any more, it was how that power was delivered.

Engine braking came as another shock to riders brought up on two-strokes. Slipper clutches were on the bikes from the start, but very quickly Yamaha decided they needed more. First came computer operated assistance for the clutch, then for 2003 a 'kicker' system to hold open two throttle butterflies - just enough to kill off some of the engine braking as the rider went down the gears.

THE FIGHT BACK

Furusawa reorganised the whole of Yamaha's racing department. The development project bikes were dumped and the focus moved solely to the race bike. Nothing much was seen for a few months but, in retrospect, we know they were already talking to Rossi and his team about moving over from Honda.

If it was clear to Yamaha they needed a star, it was also clear that they would need a motorcycle for him to ride. The first evidence that big changes were coming was at the Valencia MotoGP at the end of 2003 when two new chassis with revised front engine mounts and inverted swingarms appeared in the factory garage. Despite having no testing time on the new chassis before the GP, both riders found them to be such an improvement that they decided to race them first time out.

There's simply no point in having a star rider and his extremely experienced back-up team if there isn't a whole selection of things for them to try. For Rossi's first test, therefore, several engines were prepared with slightly different specifications and, to Yamaha's delight, Valentino chose the one they'd hoped he would most like. This had a new four-valve cylinder head and a new firing order, an engine that made usable power and provided traction.

The target was for a year's development, with Valentino and his team hopefully grabbing a few wins towards the end of the year, then to aim for the World Championship in 2005. Anything more would be a bonus.

AT THE RACES...

So, enough of the preparations, what exactly happened when Rossi and his crew turned up to ride the bike? During testing the chassis set-up was also radically changed, with the bike being made longer and higher. Compare pictures of last year's bike with this year's version and it's clear that the forks are nearly 25mm longer and the swingarm longer by the same amount.

These modifications were done to a chassis that had even more radical front engine mounts than the ones in use at Valencia at the end of 2003. Front forks don't work so well when leaned over, so to try and maintain grip the new chassis allows the whole headstock to flex a little when the bike is deep into a corner and leaned right over.

The initial chassis changes were relatively easy to spot. Only Rossi had them on the first day of final tests at Catalunya, but by the second day Checa had the same set-up. The World Champion went on to set the fastest lap in this psychologically important pre-season practice session. Jerry Burgess was uncharacteristically generous to the opposition, pointing out that Valentino was only fastest because they had a set-up for the single lap sprint and, come racing, they would be struggling...

Yamaha might have provided a kit of parts, but it was Rossi and Burgess who knitted them together. Burgess takes up the story: 'We identified fairly early what the problems were. The bike was developed by two very good 250 riders; no slur on them, but what you want for a big bike, a 500 or a four-stroke, is something different. All bikes operate within a circle and the circle wasn't anywhere near where I felt it should be. With a rider like Valentino you are getting good information. If you had asked me to make that big a step at Honda I would have been conscious that we had never been in that area, but being a new bike we weren't in the area so very big steps had to be taken. To ride one of these things right you need to have enough feel to get the bike to slide; you must be able to feel your way into a slide and then back out again safely.'

A longer bike required more rider input to arrive at perfect traction, but the point of having the bike longer was that the rider could choose to increase or reduce traction by moving his weight forwards or backwards. By having the bike taller, they could run it as a more stable chassis but one whose higher centre of gravity would still allow it to turn into corners quickly. Masao Furusawa: 'For sure we have built a bike that Valentino has to move around on to get the best out of, but our final goal is to build a bike where the rider doesn't need to move as much.'

Burgess's game plan was to find a good basic set-up, then work his way through the bike finding the optimum settings for each major variable. 'You have to take all the good things you find and make them work. Some guys will find a chassis setting that will, say, allow more rear-wheel grip but upset the front. Rather than persevere they'll go back to the previous settings. I want that advantage, though; we will try to find a way to have that advantage and make the front end work as well.'

Rossi has never stopped looking for optimum traction. Once a basic set-up had been found - let's call it the long-wheelbase version, the one used for the South African win - the team revised the settings. The long-wheelbase variant was clearly easy to control but possibly didn't offer the best traction. After the race at Jerez, where Rossi had clearly found the bike a handful in the wet, the chain was shortened and efforts made to get the bike to work. If they could get satisfactory control from the slightly shorter bike then they would have more grip: getting the bike to react well looked to be the problem.

(Left: Note welding on the inside of the swingarm. This sort of modification only appeared on Rossi’s and Checa’s bikes as Yamaha searched for the stiffness ratios that would let the bike slide controllably. Right: Test swingarm at Catalunya test pre-season. Note the swingarm pivot is set high in its adjustment range - whete it stayed most of the year.)

At Le Mans, two weeks later, Rossi rolled out the short-wheelbase bike. It wasn't the best meeting to try this out as the machine just didn't want to behave. It stayed'short' throughout practice and then, just for the qualifying laps, the longer set-up came out. It was the shorter version again for the race, but it was clear that something wasnt quite right. Burgess again: 'We tried to get the bike right but we just ran out of time. We made a right Horlicks of it.'

Yamaha's determination to win was quite obvious at Le Mans, but the French track is demanding, with a lot of straight-line braking and acceleration. Race engines can be built specifically for each circuit - but it's not done all the time because it's not cheap - and if you were really trying you would build engines with more compression to tip the balance of the bikes capabilities towards acceleration. All the Yamahas at Le Mans had starting difficulties, just what might be expected from a very high-compression engine.

From the outside it looked as if the resulting set-up was snappy, with Rossis bike looking very nervous, very twitchy. By the next round, at Mugello, there was a new swingarm, another was tested after the Catalunya race, with chassis composure increasing each time. A new chassis arrived for Assen. All of these modifications proved very difficult to spot in the metal, but with the standard chassis allowing a wide range of geometry options the most likely ditferences were the changes in flexibility given by each new part.

Rossi's set-up might not have appeared to change much more until the last few rounds, but the bike was certainly being changed inside. Burgess was doing what he does best, finding the right combination of chassis, suspension, gearing and engine settings to give Valentino the best possible tool with which to work his magic. Grip and traction were the main targets. The rear tyre hook up that allowed Rossi to get ahead of Gibernau at Mugello and Catalunya and netted him wins at those circuits which should have favoured the mare powerful Honda; the gearing choices at Donington that allowed a seamless start and run out of Redgate and down the Craner Curves - all were classic, old-fashioned racecraft in action.

Towards the end of the year further evidence of Yamaha's extremely pragmatic approach became obvious. Qatar held its first GP in previously unheard-of temperatures, over 55 degrees Centigrade on the track. To help cope with this terrific heat the works Yamahas suddenly sprouted additional air dams side fairings designed to deflect more air into the radiator and spoilers to help drag hot air out again. The radiator itself looked thicker too. And all these things added drag and slowed the bike It might appear that this was a panic measure, but the reality was that the Yamaha only carries enough radiator and ducting for 15 of the 16 races. Designing adequate ducting to extract hot radiator exhaust is one of the bigger challenges for bikes with wide-at-the-front, in-line. four-cylinder engines. It's better to have a small frontal area and low-drag fairing for 15 races and take a penalty at one round than to design a bike that has a less efficient fairing and a bigger radiator that Isn't needed most of the time.

(The loud bike (seen from both left and right) with the short exhaust pipes that Rossi tested and that made a brief appearance at the last race of the year - after the title had been won)

(The narrow-bodywork bike that Checa (and Rossi) tested at Brno. All bodywork is different and the fish mouth air intake makes it instantly recognisable. More significantly, you cannot see any of the carbon-fibre airbox between the frame and the tank)

By the end of the year Burgess's careful work through the set-up of the bike saw him start to change the swingarm pivot position.it had always been adjustable, but it was left alone while the rest of the bike was worked on.

By round 14, in Malaysia, the pivot position had gone up over 5mm.That's a pretty big change, whose effect is to force the rear wheel into the ground under power and, all other things being equal, it has the potential to make the bike less stable under hard deceleration. In less grippy situations there might be more slides, but if you can get it to grip then you have the advantage.

The Yamaha never really came across as a finished project and the bike never, except in the hands of Valentino Rossi, seemed to have the upper hand. It's certainly not yet the best motorcycle in pit lane. What was on view in 2004 was a very carefully considered evolution of an existing bike, its performance in 2005 will be another matter entirely.

(Just because you need to lengthen the forks doesn't mean you want to alter spring length or air gap. Yamaha's solution to that problem was just to extend the outer tube.)

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THE FIRING ORDER

Furusawa had very different views on the sort of power that would allow the Yamaha to get up to the front: 'We took a long look at the problem and optimised the combustion timing. No two cylinders fire together. In Japan we have the Shinkansen trains [bullet trainst, very fast trains running on steel wheels, there is very little traction but still the power gets through. This is because the torque from an electric motor is very smooth. Just go and ask Valentino or Carlos, the engine they have is very smooth and that is what they need in order to have speed in the corners.'

With his optimised tinne order engine rurusswa nas basically reinvented the in-line four as a GP motorcycle power plant. A classic in-line four has a crank that provides four firing pulses every four-stroke cycle. On a normal Brine tour couady sizeo puises ane every Tou degrees of crank rotation. It seems that at 240bhp the tyres find these fluctuations a real problem. Honda were clearly getting their power to the ground without too much difficulty, but as a side effect of their 75.5-degree vee-engine layout. Assuming they have four cylinders on a 360-degree crank, they had a firing order that gave a second pulse 75.5 degrees after the first, and on one rev another pulse about 50 degrees further on as the fifth cylinder chimed in. So why do vee engines get their power down more easily?

In normal engines, crankshafts do not rotate at a constant rate. During each revolution they slow down and speed up a little, depending upon what's going on above the piston. As the piston comes up on the compression stroke it first has to compress the basic mixture and then, before it gets to TDC, It suffers the initial effects of the spark plug setting off the mixture: as this happens the rate of crank rotation slows slightly.

As the piston goes over TDC, the full force of the combustion hits and it accelerates down again, speeding the crank back up. On a 180-degree crank four there are four slow-down, speed up' sessions every two rev cycle. If, however, the crankshaft is rephased so that the second piston arrives at TDC Just 40-50 degrees after the first, its slow-down' session is effectively cancelled out by the first of the close-running pair shooting away from TDC after its mixture has been ignited. From the point of view of the tyres it gets a series of long pushes without grip-damaging torque peaks and a much smaller number of crank speed fluctuations - albeit the fluctuations are bigger than with a normal 180-degree layout. Rather than describing the motor as sog bang, then, we should consider using the term long bang'! All these benefits help the tyre find grip. With the RC211V, Honda had it all along.

Where Furusawa-san and his team were fortunate was in the original desion team's decision to reverse the rotation of the crank. To do this they added a shaft just behind and above the crankshaft. in the original engines it just reversed the direction of rotation and drove the alternator; in the new 2004 engine it also worked as a balance shaft.

WHY REVERSE THE CRANK ROTATION?

The original design team reversed the rotation of the crank to make the bike more agile. Yamaha uses the crank to cancel out some of the gyroscopic stability imparted by the wheels. (Normally the gyroscopic effect of the crank is added to that of the wheels but in this case it’s taken away.) This feeling of agility means the rider doesn't notice the effort of rolling that crankshaft over into a corner.

A full description requires an understanding of gyroscopic forces and the way a motorcycle initiates a turn, so just borrow a friend's mountain bike wheel and hold it out in front of you as if your arms were a pair of fork legs. Turn the wheel as if the rider had quickly turned the bars left, and you will discover the top of the wheel trying to roll right, which would start the bike into a right-hand corner. At this point the whole of the motorcycle trips over the front wheel and the bike slams over to the right. As the bike rolls in, a second gyroscopic reaction occurs and the wheels try to oversteer, thus turning into the corner. Try turning a spinning bicycle wheel over 45 degrees too! The Yamaha's crank, by turing backwards, reduces this effect. This means that the bike turns neutrally, has less initial gyroscopic stability and, once turning, less oversteer.

One critical cost of this design is that the extra shaft required to let the crank turn backwards costs power: typically, an extra gear-set costs about 2 per cent of available power. The cost of the Yamaha's agility, therefore, is about 5bhp - 5bhp that could usefully be used down the straight.

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