First shot in the four-stroke revolution: Doug Henry's SX win 20 years ago in Vegas

May 05, 2017

The view of the Pacific Northwest tall pines seen from the large windows of Duke Finch’s motorhome was stunning.

Following a race in late August of 1996, Doug Henry was sitting with Finch, the race director of the AMA Pro Motocross series. He decided at that moment he would get his own motorhome and take his family on the road with him to the races the following season. That panoramic vista a few miles north of the Columbia River was part of what inspired Henry to keep racing at all.

Before the day had started, before he won the second moto of the 1996 Washougal Pro Motocross National, Henry hadn’t won anything in 15 months. In 12 of the 18 races prior to Washougal, he had finished outside the top 10. He didn’t know he was going to struggle that hard after his June 1995 back injury. That single moto victory gave him the confidence to keep going and one month later he met with Keith McCarty, Yamaha’s team manager, to talk about a new contract.

Doug Henry
Doug Henry celebrates a win in 1993. He almost called it quits before the 1997 season. Photo by Henny Ray Abrams.
“I went to Keith’s house because I decided I wanted to race another year,” Henry said. That’s when McCarty asked Doug to ride a prototype four-stroke motorcycle that Yamaha was developing and wanted to try in the 1997 AMA Pro Motocross championships.

McCarty himself had only recently heard of the project and he hadn’t even seen it yet. Earlier that year, he shipped two full factory race bikes — a YZ125 and YZ250 — to Japan, but he didn’t know why. He later learned that those race bikes were both a development aide and a barometer for what became known as the Yamaha YZM400F (OWH2), a one-off prototype four-stroke motocross race bike.

McCarty had nothing to give or show Henry except the trust the two men had built between them. Doug was torn because he felt like he would be starting all over after building himself back up from his near-career-ending injury. Also, the Supercross and motocross seasons still overlapped in those years. Henry would be bouncing back and forth between two completely different bikes, riding the two-stroke in Supercross because the YZM would not be ready for the opener. Henry left McCarty’s house without giving him an answer.

“I don’t know that we had a plan B,” McCarty said when asked who the alternative rider would have been if Doug had declined. “I think he was appreciative that we believed in him. If anybody could make it work it was him.”

Yamaha YZM400
The Yamaha YZM400F prototype Doug Henry raced to victory at Las Vegas 20 years ago this month. AMA photo.

A Yamaha engineer with a plan

At some point in the mid-1990s, a panel at Yamaha of Japan listened to a proposal from Masakazu Shiohara, an engineer who had been involved in designing two-stroke engines for Yamaha’s 500 cc GP world championship race bikes. He wanted to develop a lightweight four-stroke motocross race bike — never mind the fact that he was neither an expert in four-stroke technology or motocross. (Shiohara later went on to design Yamaha's YZR-M1 when the 500 cc GP championship switched to four-strokes and became MotoGP).

Shiohara and his team knew they wanted their bike to be based on the geometry of the YZ250 and they started by simply mounting a 28-horsepower TT250R trail bike motor into a YZ250 frame. According to an account on Yamaha’s corporate website:

“They were at a dead end until one of the engineers on the development team, Kenji Tamura, made an interesting proposal. He took the cylinder head and camshaft of a YZF750 engine and sawed off the sections for a single cylinder. He then paired it to the cylinder of a TT250R engine (YZF bore: 72 mm; TT250R bore: 73 mm) using welding and putty to make a prototype 250 cc engine. The engine revved up to 13,000 rpm and had power roughly between that of a 125 cc and 250 cc two-stroke engine. When this prototype engine was mounted in a YZ250 frame, it ran unexpectedly well and weighed just under 110 kg — this could work!”

AMA rule book
Yamaha was the first to win a race by taking advantage of the larger displacement the AMA rule book allowed for four-strokes. Image from AMA rule book.

AMA Pro Racing rules (at the time) allowed for four-stroke motorcycles up to 550 cc to compete in what was then called the 250 class. The Yamaha engineers decided the power of a 550 would be meaningless if the bike was too heavy. Plus, they wanted to fit the engine in the YZ250-based chassis. They calculated that two-stroke motorcycle engines produce 1.6 times the power of four strokes, which led them to a displacement of 400 cc with a bore and stroke of 95 mm by 56 mm. The bike produced 50 horsepower.

While Henry was back in the United States mulling over what he was going to decide to ride in 1997, engineers in Japan were assembling one of the most exotic off-road race bikes of all time. The engine was machined from a solid block of billet aluminum. It didn’t even have an oil drain plug in the bottom. The rest of the hand-fabricated pieces were a mixture of the sexy elements from the periodic table: magnesium, titanium, chromium/molybdenum (Chromoly) and carbon fiber. In their March 1997 issue, Motocross Action wrote that it was “assumed” the bike cost $500,000 to make but no one at Yamaha today can confirm that.

Yamaha was certain they would race the bike in the 500 cc World Motocross Championships (MX1) in 1997 with Andrea Bartolini and Peter Johansson. That series has no production rule. But to compete in the United States, Yamaha needed permission from the American Motorcyclist Association to break the production rule, which states that OEMs must race homologated motorcycles based on production models. Yamaha of USA simply told the AMA what they were doing and what they needed and, shockingly, were given the thumbs up. In the January 15, 1997 edition of Cycle News, the exemption was explained:

“With an eye toward the future the AMA has given the manufacturers a one-year 'coupon' — redeemable in the year of their choice — to develop a machine of this type.”

Doug Henry on the Yamaha YZM400F
Doug Henry races the Yamaha YZM400F in the outdoor motocross season at Binghamton, but it was his win in the final round of Supercross that launched the four-stroke revolution. Photo by Paul Buckley.

This meant that Yamaha didn’t need to have 400 units of the YZM400 made available for sale and each OEM brand could have one year of their choosing to compete on a prototype. They only had to meet minimum weight (216 pounds), sound (102 decibels at the time) and use the same race fuel as the two-strokes.

Merrill Vanderslice, AMA Pro Racing’s vice president explained in an issue of American Motorcyclist: “[The production rule] was hindering development of four-stroke technology at a time when many people think that could be the direction of racing in the future. That’s why we agreed to offer one-time exemptions.”

Doug Henry
Doug Henry at the Atlanta Supercross round in 1993, when only two-strokes roamed the motocross earth. Photo by Henny Ray Abrams.
Doug Henry eventually said “yes” to McCarty. He went home to Connecticut and bought a Husaberg FC510, a monster of a four-stroke that Joel Smets had been winning on in the 500 cc World Motocross Championships. It ended up being nothing like the YZM400F that Henry finally got to ride months later in Japan, but he knew he needed to feel the rotating mass and power delivery of a four-stroke. He took it to “The Dam,” a brutal rocky, sandy and whooped-out riding spot in Connecticut that molded Henry into the tough and gritty rider he was.

“It was like riding a pogo stick!” Henry recalls. “A tall, fast pogo stick. I’m sure I took it to my suspension guy right away.”

At Supercross round nine of 15 in March, Henry broke his hand, a small but frustrating fracture because at the time he was in second place in the championship, only four points behind Jeff Emig. In early March, he debuted the YZM400F at the motocross opener (eighth) and raced it again at rounds two and three (fourth and sixth) in early May, the first races back from his hand injury. Being eliminated from the points in Supercross, there was no use in going back to the YZ250 two-stroke for the season finale.

The team decided to take the prototype to Las Vegas and try to steal some thunder from the bigger conversation, which centered around the battle between Emig and Jeremy McGrath for the championship.

Ready to roll the dice in Vegas

On May 15, a long, hot practice day at Carlsbad Raceway, Henry knew he had a great bike. He also had a bog in the engine that scared him. They were frustrated and losing light and the bike still had to go 70 miles back up I-5 to Cypress, California, in order to get prepped for practice in Las Vegas the next afternoon. Bob Oliver, Team Yamaha’s engine developer and fabricator, discovered that the accelerator pump was expelling too much fuel. Oliver went to work with what he had in the test truck.

“I made an adjustable screw with a locknut underneath the diaphragm,” Oliver said. “We had the ability to adjust this thing from the bottom and we put an O-ring on it.” The team left Carlsbad happy and confident.

Meanwhile, in Las Vegas, Roy Janson was searching for ways to keep the dust down on the race track PACE Motor Sports had built. They had experimented with additives before but this time tried something new: magnesium chloride, a compound used for both de-icing and dust control on roadways. They didn’t know how much to put down. With a garden hose off the back of a water truck, the track crew sprayed a full tank of a diluted mixture.

The next morning, they realized they had overdone it. The track, while completely dust free, was sealed and hard as concrete. Even the tops of the jumps had rubber on them.

“If you were on a bike that did better in slippery conditions, this was the night to debut it,” Janson said.

Forgotten in time was the fact that Henry was riding one of four thumpers competing that night in Las Vegas. Guy Cooper and Shaun Kalos showed up on Husabergs and Lance Smail raced a KTM built by Tom Moen. KTM was actually the first OEM to take advantage of the four-stroke exemption rule and Smail had been competing on a works KTM 550SX all season, qualifying for several main events. In Vegas, however, Henry was the only rider on a four-stroke to qualify.

Henry remembers the excitement of the spectators who came up to the Team Yamaha area. He was already a bit of a folk hero, for his humble, hard-working roots and comeback story. Now, he was reaching a completely different genre of enthusiast: the four-stroke fanatic. In the main event, he led every single lap and split all the headlines and column inches with Jeff Emig, who stopped Jeremy McGrath from winning a fifth straight championship.

McCarty and Oliver don’t have any strong standout memories from that night’s main event outside of counting the laps and the excitement of winning, which is normal for them on any weekend. For Henry, it’s a major highlight from a career filled with historical memories.

“We were all like, ‘I can’t believe that just happened. I can’t believe we just won a Supercross on this bike the first time out,’” Henry said in a heritage video produced by Yamaha in 2016.

The residual effects and the significance of the moment make Henry wonder how he would rather be remembered — as just another Supercross champion or as a history maker, the first rider to win a main event on a four-stroke. No matter what side of the white-hot two- vs. four-stroke debate you’re on, two decades ago, Yamaha and Doug Henry did something that significantly changed motorcycle racing.

To think, he could have said “no.”