In 1998, Roger DeCoster was still on staff at Dirt Bike, a position he held since 1994.  He was also Suzuki’s Race Team Manager by then. That gave him a vested interest in the rules that allowed four-strokes a displacement advantage in Pro motocross–at the time, Suzuki had no plans for a four-stroke motocross bike, although the DR-Z off-road project was then underway. In the May, 1998 issue he wrote  the following column expressing his displeasure with the displacement advantage that Yamaha had.


Should four-strokes be given a displacement advantage for racing? It depends on your idea of what racing is all about. In my mind, racing is all about letting the best man win. Rules that promote this are good rules. Rules that don’t are bad. Motocross has actually managed to stay pretty pure in that respect over the years. At first, a racer could use anything he wanted as long as it was under 500cc; it didn’t matter if it had one cylinder or six, or if it weighed 50 pounds or 500. In those days, everyone used four-stroke singles because they made the most suitable power and were the most reliable. In the search for more power, some riders started adapting road-racing engines to MX–engines from the AJS 7R, the Matchless G50. Some even used Norton Manx road-race powerplants. Later there was a period when Triumph Twins were popular, mostly in the Famous Rickman Metisse chassis.

In the meantime, a 250cc class was born. It didn’t have the interest or the prestige of the 500 class, but it did provide the opportunity for some different engine designs to come into play–most notably the two-strokes. At first, two-strokes were the joke of the paddock. They sounded funny, they were terribly temperamental and unreliable. If a two-stroke rider stalled his bike in a race, you would see him lap after lap with his fuel-flooded bike on its side and the gas petcock closed, trying to get it cleaned out. A cloud of blue smoke would hang over the whole scene. It was a comically common sight. In those days, promoters loved to throw stream crossings into the course, and usually the main line would be clogged with drowned-out two-strokes.

Doug Henry switched to a production bike after Yamaha’s one-year exemption was passed. Four-strokes were still allowed a displacement advantage.

Yet, with all those shortcomings, special rules were never used to give two-strokes any kind of advantage. They were never given extra displacement. They were never given a head start. The four-stroke riders didn’t have to wear blindfolds or start backward. Two-strokes became competitive on their own. First two-strokes took over the 250 class, and eventually made an impact on the 500 class. Jeff Smith was the last four-stroke rider of that era to win before the two-strokes dominated.

The age of the big two-stroke started with Paul Friedrich in ’66 and lasted almost 30 years, until Jacky Martens won the championship on a four-stroke in Husqvarna ’93. That brings us to ’98, with Doug Henry making his presence known on the American racing scene with the YZ400F thumper.

This time around, however, it isn’t engineers who are making the change occur; it is the rule makers. The AMA and FIM amended the rules allowing four-strokes to have more displacement than two-strokes in every class. There are lots of reasons to support this: crowds love the sound of four-strokes; new emissions regulations are forth-coming; four-strokes are the engine of the future, so we might as well get ready, and so on. These are all based on good intentions, but doesn’t the AMA have enough things to worry about without taking on the burden of meeting the new emission standards? Isn’t that the problem of the manufacturers? If that’s a legitimate reason, then why aren’t these oversized four-strokes required to actually pass the emission standards before entering a race?

middle content two stroke

Trying to level the playing field is a good goal, but how do you decide what is truly level? There’s no scientific formula for comparing two-strokes to four-strokes. The AMA lets 550cc four-strokes race against 250cc two-strokes, and 250cc thumpers race 125s. The FIM puts 360cc four-strokes in the 250 class. There’s no way to come up with a universal formula because the bike that gets the most development will always be the most competitive. Right now, two-strokes are on top because they received all the development in the ’70s and ’80s. Then European manufacturers like Husqvarna, Husaberg and KTM saw an opportunity to stimulate four-stroke sales with racing success.

That opportunity came about mostly because the 500 class had become less competitive as the Japanese companies slowly pulled out. Still, the attention that these manufacturers received must have stimulated Yamaha. If tiny Husaberg got so much interest from its thumper program, then think of the success that a massive company like Yamaha could earn. Yamaha certainly did a great job, both on the works bike on which Henry won the Las Vegas Supercross and the production version.

Too bad we couldn’t see into the future in ’96 when the AMA approved the displacement spread. At that time, no one took four-strokes seriously. No one thought that four-stroke development would be carried out by anyone other than a few tiny companies with microscopic R&D budgets. Even Yamaha’s race team officials probably didn’t know what was going on in Japan. All that changed after Las Vegas, though. It isn’t that Doug Henry has a big advantage over the rest of the field–quite the opposite. It seems he has to push harder and take more chances than any of the other top riders. But he clearly has more power–isn’t that why they invented classes to start with? Now that the rule has passed, it’s hard to go back. During the last meeting, Yamaha raised a legitimate point: After the company has spent thousands of dollars on the project, it wouldn’t be fair to change the rules. Kawasaki’s Bruce Stjernstrom thinks that displacement rules should be absolute, that 250cc two-strokes should race against 250cc four-strokes. Team Honda’s position is that four-strokes should be segregated into another class. Neither solution seems likely for now.

I can’t help but wonder what would happen if some top executive at Honda got really mad and decided to go all-out just to prove a point. Certainly, Honda has the resources to finance a project that no one else could match. There are not enough MX bikes sold to justify a project like that on an economic basis, but Honda has been known to launch such operations on corporate pride. Maybe it’s already happening with 250 four-strokes aimed at the 125 class.

For now, I think a compromise is in order. The AMA and the FIM need to agree on a displacement gap. Perhaps putting the four-stroke cap at 360cc, as the FIM does now, would be unfair to Yamaha. But we should at least move the AMA limit down to 400cc.

More than anything else, though, we need to be ready to change-and keep from painting ourselves into a corner–again.

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