GPmoto Garage recreates Honda’s 1991 “Stealth Boomer”…
In the 1990 Baja 1000, Honda’s XR600R entry ran a near flawless race against the mighty Kawasaki KX500 two-strokes…and still lost, keeping pace in the rough sections but losing as much as three minutes in the faster stretches. It was clear the XR needed more speed and power.
Engineers began working nights and weekends to build an XR600R that could take the fight to the two-strokes, and Honda soon made it an official project. The driving force behind the facotry racer’s development was legendary off-road racer Bruce Ogilvie, team manager for American Honda’s off-road racing efforts.
“In 1991 we developed the bike and called it The Monster.”
The XR667 “Monster” was loaded with trick features: big fin head, oil quick-fill from an RC30 endurance racer, oil cooler, 210-watt power output, aluminum tank with Drybreak quick-fill opening, custom removable subframe with aluminum airbox and hinged filter door, quick-release custom fairing for high-speed riding, 43mm conventional forks with CR-length travel and CR front brake, and more.
Engine displacement was boosted to 667cc, and the newfound power made for a steep learning curve:
“We were looking for a way to gain an advantage on the big power of two-stroke bikes, so we took an XR600R and bumped the displacement…and used a higher camshaft, wow how strong it was! We really had to recalibrate our brains and change our riding style, because the speed had really increased, and we weren’t used to it.” -Bruce Ogilvie
While the bike was incredibly fast, easily keeping pace with the KX500 two-strokes, the power output proved more than the rest of the bike could bear. Cases broke horizontally, swingarms were bent, and rear wheels smashed. It was a fatal overdose of horsepower. Said Ogilvie:
“It was faster than any 2-stroke ever, but we had processed it too much, going too far beyond the structural limits of the original design of the whole bike.”
Though the Monster failed to finish the race, Ogilvie stressed that Honda learned an incredible amount from their Baja Monster.
Those learnings paid off in 1997, when Johnny Campbell won the Baja 1000 on an XR600R…and Honda went on to win 17 Baja 1000’s in a row with the XR600R, XR650R, and CRF450R.
Over the last several years, our friend Matteo Gualandi of Italy’s GPgarage Moto has been slowly building his collection of Honda Baja race replicas, including his Johnny Campbell XR628R and ’94 XR680R we previously featured.
When we say “building,” we truly mean it, as Matteo has had to scour old magazines, interviews, and museums to recreate these exotic factory prototypes, fabricating many of the one-off parts in his workshop, which also fields a pair of modern CRF racers in the Italian Rally Championship.
In their feature of the 1991 XR667, Cycle World dubbed it the “Stealth Boomer” — a testament to the massive research and development that went into the project. Says Matteo:
“For me it was like the Sacro Graal [Holy Grail], the most complicated Baja replica and that’s why I saved it for last.”
The custom fabrication that went into recreating this Baja Monster was extensive, including the one-off fairing, aluminum tank, oil cooler, custom exhaust, detachable subframe with aluminum airbox, CNC swingarm, big-fin head, 660cc big bore kit, and much more. Those with keen eyes will spot all manner of fine details, such as the anodized blue engine guard, rear brake guard, plastic fork guards, and more.
We’re thrilled to feature this stunning recreation of Baja history, and something of a tribute to the late Bruce Ogilvie — the only man to win the Baja 1000 in four separate decades. We’re sure he’d love to twist the throttle on this big-bore thumper if he were here.
Below, we talk to Matteo for more details on the Baja Monster.
Honda XR667 Baja Monster: Builder Interview
• What’s the make, model, and year of the bike?
Honda XR600R, 1991.
• Why was this bike built?
• What was the design concept and what influenced the build?
It’s a replica of the first factory Honda Baja bike. Developed by the legendary Bruce Ogilvie.
• What custom work was done to the bike?
A lot 😀 Custom fairing, oil radiator kit, aluminum tank, custom exhaust, aluminum airbox, detachable rear frame.
CNC swingarm, oil decanter kit, 660cc engine kit, big fins head.
• Does the bike have a nickname?
• Can you tell us what it’s like to ride this bike?
We only exhibited it at a fair and now we are finishing the engine, which was not ready yet.
• Was there anything done during this build that you are particularly proud of?
Yes! Everything ????, for me it was like the Sacro Graal (Holy Grail), the most complicated Baja replica and that’s why I saved it for last.