Carson Brown loves to ride dirt bikes! It doesn’t matter the year, make or model, he just loves two wheels and an engine. Lucky for us, we like showcasing his talents on said dirt bikes. Lately, Carson and his dad, BBR Motorsports cofounder Duane Brown, have been resurrecting older iconic two-strokes. This 1997 CR500 build started about two years ago when, in Duane’s words, “Carson just showed up to the house with this beater Honda CR500 in the back of his truck one day saying he wanted to rebuild it.” Naturally, Duane was 100 percent on board and the sparks started to fly.
This build started out just like every other build—with a complete tear-down and inspection. The frame and subframe were reinforced by Duane himself, then sent off to American Powder Coating to make it pretty again. The aluminum gas tank was completely hand-fabricated by Duane and Carson. This unit is slimmer and shorter than the plastic OEM Honda version.
Another item that received a huge amount of fabrication time was the swingarm. As you can see, it’s reminiscent of what you would see on full factory bikes back in the late ’80s and early ’90s. The radiators are also custom oversized models to provide additional cooling for the highly modified engine. The suspension on this machine was buried in a well-known Honda test rider’s garage for decades and are period-correct A-Kit Kayaba components that were rebuilt, but all the factory valving remained untouched.
A complete billet-aluminum Phil Denton rear shock linkage and axles at both ends replaced the OEM Honda units. Other bolt-on companies included on the chassis are Dunlop, Dubya USA, Renthal, Boyesen, MotoStuff, Works Connection and Bolt Hardware.
The engine did receive a lot of attention from Bryan Hugaburg at Red Barn Racing. As a matter of fact, we could write an entire story on just that. Here is an overview on the engine building process directly from Hugaburg: “Starting with Built 500 billet aluminum cases, these were needed for Carson’s build, as his OE center case was cracked where the main-shaft bearing seats in the case. The bearing would literally fall out of the case. Turns out, this is a problem with OE CR500 center cases and one of the reasons why Built 500 makes their cases. I had to grind slightly just under the cylinder deck for clearance to the connecting rod. They may clear an OE rod, but they didn’t clear the Crank Works Pro Rod.
“There is plenty of material in the Built 500 cases to grind without compromising strength. Also, with Built 500 cases, make sure your shifter shaft is as straight as you can get it. Built 500 puts extra support in for the shift shaft, which is great, but the shaft had better be straight or it will bind. I had to straighten Carson’s before it would fit properly.
“The cylinder is a 1989 cylinder. I like the cylinders from approximately ’87 to ’91, which are the best. The dimensions of the transfer ports, especially the boost port, are a little better for custom work in my opinion. None the less, the transfer ports still need to be evened up from side to side. The exhaust ports are too small on CR500 cylinders, and this cylinder is both raised a bit and widened as far as the Vertex piston would allow. All ports are hand-chamfered with a diamond file. The Nikasil-plated steel liner makes the diamond file mandatory. The head is re-profiled with the goal of getting an effective quench band around the cylinder.
“As CR500s are built from the OE, the quench clearance is so wide that it really does nothing to help the combustion process. The chamber is re-profiled to open it up and narrow the squish band some. Then, the head deck is milled down to bring the compression back to stock and tighten the quench clearance up. It ends up with a quench clearance about half of the original clearance at the outside edge when complete.
“We used a Boyesen Rad Valve that is ported out to match the 41mm Keihin PWK carburetor that also received a couple of modifications. First, a STIC Super-Torque metering block is added to help atomize the fuel better than the OE Keihin metering system. Second, a Thunder Products IntelaJet is added to further spread out the engine speed range over which the carburetor will provide a properly atomized fuel mixture.”
If you ask the Browns about this build, they would say it’s all about the engine, and on any other CR500 build we would have to agree with them because the specifications are insane. But, in our minds, this build has it all—custom-fabricated aluminum parts in multiple places throughout the build, A-Kit factory suspension from the era, CNC-machined billet-aluminum cases from Built 500, custom engine covers, and off-the-shelf products from Pro Circuit and Boyesen with a ton of engine performance produced by Bryan Hugaburg at Red Barn Racing.
Everyone who came in contact with this bike smiled and shook their heads in disbelief. If those facts aren’t enough to get your blood flowing, don’t worry, because we have more. Would you like to see Carson Brown at the controls during a private track rental? The head of our video department, Travis Fant, has you covered. Go to our YouTube channel and search “Return of the Honda CR500 Two-Stroke” to see it in action.