Today, 500cc two-strokes are typically found in museums or collecting dust in garages. There aren’t many current riders who regularly swing a leg over a 500cc monster. Kawasaki stopped producing the KX500 in 2004, Honda ditched the CR500 in 2001, and Yamaha’s WR500 disappeared back in 1993. These bikes earned a reputation as fire-breathing beasts—machines only a handful of riders, such as Carson Brown, Tyler Bowers, Sean Collier and Travis Pastrana, can truly tame today.

BRC Racing is a Canadian manufacturer focused entirely on high-performance two-stroke technology, and they have carved out their own niche by bringing the 500 back in a way that actually makes sense. They first made their name with KTM-based 500 conversion kits, including the Gen 1 engine we tested six years ago with Jarrett King. Since then, they’ve refined that platform and expanded to building engine kits for Yamaha YZ250 frames, bringing modern engineering to one of the most popular two-stroke chassis ever made. Their Yamaha-based YZM500 is a dropin conversion that delivers nearly 500cc of explosive power—over 60 horsepower and more than 50 pound-feet of torque—while still being tailored for real-world rideability instead of pure intimidation. Jarrett King brought our first BRC Racing build down from Canada six years ago, and now he’s back with BRC’s latest and greatest YZM500 engine kit.

The BRC Racing YZM500 engine doesn’t require any fabrication work to fit into the Yamaha two-stroke aluminum frame; this means it fits 2005 through 2026 models. It also fits into the steel YZ250 chassis models, from 1999-2004.

Josh and Kory were the first-ever dirt bike/Monster Truck duo to drift through Talladega side by side.

The first surprise came before we even left the pits. With the decompression button built into the cylinder, the YZM500 fired up easily, usually on the first or second kick. Anyone who has ever kicked an old-school 500 will immediately appreciate that detail. Once running, vibration was minimal thanks to BRC’s integral counterbalance shaft, which cancels out the harsh vibrations that plagued the original KX500 and CR500. This alone makes the engine feel far more modern than its predecessors.

On the track, the power delivery really separates the YZM500 from the 500s of the past. Instead of producing a sudden, violent hit, the BRC engine uses a simple pneumatic power-valve system with a triple-blade design that creates a long, smooth and linear power curve. It still has massive torque and pulls hard everywhere, but it does so in a way that’s usable. You can ride it aggressively without constantly feeling like the bike is trying to get away from you. It’s a true modern 500—still wild but controlled.

The BRC top end and cases accept your donor Yamaha YZ250 or YZ250X gearbox, and it encourages you to actually shift. Third gear worked well on much of the track, but when it was time to stretch the bike’s legs, fourth was the right choice. It did lack some of the explosive power that the oldschool 500cc two-strokes were known for, thus the bike couldn’t be lugged around corners in third gear. In tighter sections, second gear was necessary to keep the engine in its sweet spot. The engine rewarded an active riding style. Our test bike ran a 14/51 gear ratio, which felt appropriate for motocross.

Suspension setup proved critical. The suspension on our test bike was on the soft side, and combined with the added weight and rotating mass of the 500cc engine, it made the bike want to push, and chug forward under braking and corner entry. While the explosive hit and lug-ability of this two-stroke engine were relatively manageable, the inertia of the big engine is still very real. Stiffer spring rates and valving would be essential for our pro test riders to get the most out of this bike.

Fitment is one of the strongest selling points of the BRC Racing YZM500 engine kit. It’s a true drop-in engine that bolts directly into Yamaha’s aluminum two-stroke frames from 2005 through 2026 with no fabrication required. It also fits 1999–2004 steelframed YZ250 chassis, though those require minor modifications. The engine mounts remain unchanged, which keeps the installation straightforward and accessible for the average builder.

Radiators are the one area that requires extra attention. Due to limited space near the power valve, the YZM500 needs modifications to both lower radiator fitting locations. BRC supplies 6061-T6 caps and fittings, and recommends having an experienced aluminum welder block off the bridge-pipe fittings and relocate them to the rear of the radiators to ensure proper clearance and cooling.

The engine itself comes complete with new cases, and a new crank, cylinder and head while using the internals of a YZ250 bottom end. The transmission, clutch, ignition and water pump are all sourced from a donor Yamaha engine, which keeps parts commonality high. Every kit includes a purpose-built exhaust pipe and silencer designed specifically for this setup, and contrary to popular belief, the stock YZ250 carburetor is the best match for this engine.

The 500cc two-strokes are known for being incredibly hard to ride. That was not the case with this YZM500.

Fueling is simple. The YZM500 runs a 50:1 premix ratio and can safely use 91-octane pump fuel, though we opted for ETS Racing’s Extrablaze 100 race fuel for cleaner combustion and an added margin of safety. Maintenance is refreshingly straightforward for a big-bore two-stroke. BRC designed the kit around readily available consumables, using a Vertex CR500 piston, a ProX CR500 rod kit, KTM bearings and seals, and Cometic gaskets that can be ordered directly through your dealer.

At $6100 for the engine kit, the YZM500 represents a surprisingly attainable path to 500cc ownership. Find a used YZ two-stroke, source a donor engine, and you can build a modern 500 without custom fabrication or unobtainable parts. For those who want a turnkey solution, BRC will assemble the kit if you provide the donor components, a service that runs roughly $1100.

Our test bike was equipped with a well-thought-out parts list. Psychic Motorsports supplied radiator hoses, clutch plates, a master cylinder rebuild kit and a Keihin carburetor rebuild kit. GBrakes handled stopping duties with steel-braided brake lines (in a Yamaha blue color) and oversized front and rear rotors, delivering a consistent and positive brake feel even under heavy use. The bike also featured ASV levers, Dunlop MX34 tires, a TM Designworks chain slider, Motion Pro cables, a D.I.D 520MX chain, Luxon triple clamps, CFR handlebars, and fresh Decal Works graphics paired with a Polisport restyle kit to modernize the look of the 2008 YZ250 chassis.

BRC Racing’s engine fits right into the Yamaha YZ chassis.

ASV’s unbreakable levers are great insurance.

GBrakes supplied the oversized front brake rotor and the steel braided hoses—in Yamaha blue.

During our testing, we made a new friend. Kory Kinal is the driver of the “Jekyll and Hyde” monster truck for the 2X Monster Trucks Live Tour. Kory is a local boy from Victorville, but the 2X Monster Trucks crew is from Kansas, and they travel all over the U.S. racing the monster trucks and doing freestyle shows. We happened to catch the perfect driver at the perfect time to put him up against the perfect bike—the YZM500 two-stroke. We like to think the “M” in BRC’s title for their Yamaha build stands for “Monster,” and after Kory got done winning the monster truck race and putting on a show for the Glen Helen crowd, he was able to knock an item off his bucket list, drifting his monster truck around the most famous turn in motocross—Glen Helen’s Talladega first turn.

Kory can do all kinds of crazy tricks with his truck, but he’s never drifted around an ultra-steep, 45-degree banked, banked, 180-degree turn, and he’s also never gone wide open in his truck with a dirt bike riding 10 feet away from him. Kory couldn’t see MXA’s Josh Mosiman next to him, but he trusted in Josh’s abilities to stay away from his five-and-a-half-foot-tall tires. Kory’s 2X Monster Trucks crew was on hand to make sure his truck was ready to go and be an extra set of eyes as he drifted the first turn a total of six times.

Was this a Monster Truck test? No. Was it cool that we drag raced the YZM500 against a monster truck? Yes. The BRC Racing 500cc just barely beat the 1500-horsepower monster truck in the first drag race. However, the monster truck is geared for short bursts of power and not all-out drag races.

The BRC Racing YZM500 isn’t just a throwback. It’s a modern interpretation of what a 500cc two-stroke should be—powerful, usable and surprisingly accessible for riders who have always wanted to own a true two-stroke monster without the downsides that once came with them.