Japanese day of reckoning for MotoGP.

The day of reckoning arrives at Suzuka on Sunday with the four-strokes late-crashing the two-stroke MotoGP party that has been going on unchallenged for almost three decades.

It is 28 years ago that British rider Phil Read brought the 500cc world title to the Italian MV Agusta factory, the last four-stroke winner of the crown. A year later, in 1975, his old team-mate, and 15 times world champion, Giacomo Agostini brought Yamaha its first 500cc title on a two-stroke machine, signalling the end of the four-stroke era.

Ironically, it was also Agostini who secured the last ever four-stroke grand prix victory when he won the 1976 West German Grand Prix at the daunting 22.835kms Nurburgring circuit, riding the three-cylinder MV Agusta.

Honda tried to redress the balance in the late seventies, but then it was 500cc versus 500cc - whether two-stroke or four-stroke. Despite the technical brilliance of the NR500 Honda, which featured oval pistons, it was just no contest. This season will be very different.

The four-strokes will be allowed engines up to 990cc, although the bigger the capacity and the more cylinders used, the heavier the machines will be compared to their two-stroke opponents. For example, the five cylinder 990cc RCV four-stroke Honda that has been leading pre-season testing with world champion Valentino Rossi at the helm, must weigh a minimum 145kg. The NSR Honda two-stroke ridden by the West Honda pairing of Loris Capirossi and Alex Barros have a weight limit of just 130kg.

So where will the four-strokes hold the advantage - and is there any hope for the smaller and more nimble two-strokes? It's a long time since the two met head-to-head on a grand prix racetrack....

Antonio Cobas, technical director of West Honda Pons, has followed the development of the new four-strokes with great interest. Not only will his NSR two-strokes be meeting them head-on at Suzuka this weekend but, next year, his team will be looking to four-stroke power to bring them world championship success. He agrees that the four-strokes hold the advantage at certain racetracks but don't rule out the two-strokes completely.

"The main difference will be the exiting from the slow corners and the top speed on the long straights," Cobas explained, "The two-stroke riders have to concentrate very hard on operating the throttle coming out of the slow corners. If they are not very careful they suddenly can be high-sided from the machine.

"On a four-stroke it's much easier, and they can just open the throttle and accelerate away. For spectators, I think that's where they will see the main difference with the four-strokes accelerating away from the two-strokes coming out of the slower corners."

However, it's not totally one-sided and, as both Loris Capirossi and Daijiro Katoh have shown in the pre-season tests in Barcelona and Suzuka, the two-strokes still hold certain advantages.

"The two-strokes - and our two riders in particular - seem to have an advantage over the four-strokes braking into a corner," revealed Cobas.

"The four-stroke is heavier, and it's not been easy for former two-stroke riders to adjust to the engine braking characteristics of a four-stroke. At the moment, the four-stroke teams are working to try and make braking easier for their riders, but that certainly is one of their problems. The difference between the two braking machines is very small, but that's where the two-stroke riders will seek a tiny advantage. They know once into the bend and on the way out the four-strokes will be superior."

The usual prophets of doom have been circling the new MotoGP championship like a flock of vultures. Why on earth change the rules after the success of the two-stroke dominated title chase? Everybody agrees the last two years have been fantastic, with races won by hundredths of a second, lap records shattered and the leads swapping six times in a single lap, but the simple fact is that the format has to change if the championship is going to?survive.

The major motorcycle manufactures such as Honda, Yamaha and Suzuki have not built larger capacity two-stroke road-going machines for some time. Despite this, they have still invested millions of dollars developing the two-stroke machines that have dominated grand prix racing since the mid- seventies. The change of rules means the major manufacturers are queuing up to build the ultimate MotoGP four-stroke machine. It's their shop window for their new generation of road machines.

We may have to bite the bullet for a couple years before we get back to the superb racing at the front we've been privileged to watch for the last couple of years but, in the long run, it's the only way ahead. Also future rule changes could bring the capacity of the machines closer together.

"Maybe we should not be analysing the difference between two-stroke and four-strokes, but 500 and 990cc machines because so much difference in capacity could be wrong," explained Cobas, who is like so many others absolutely is certain that four-strokes are the future of MotoGP.

"For sure, I'm very excited, and it gives all of us the opportunity to work in different ways. And, from a technical point of view, it's very exciting. We have to have four-strokes in our team next year."

Cobas tips the four-strokes to do well at the season opener in Japan next weekend, with their superior power paying dividends on the tricky Suzuka circuit.

"It's too early to know everything, but fast tracks should suit the four-strokes with their extra power and acceleration out of tight corners," he said, "That means the four-strokes will go well at Suzuka, with it's long straight and the last corner where the bikes accelerate from almost zero.

"Both these things on the same track will make it tough for the two-strokes. Suzuka has many different types of corners and it's a very special track. Last year, Loris Capirossi put in a very fast pole setting lap, which we thought at then time would stand for many years - but who knows this year."