Based in Florida, USA, Cohn Racers is mostly known for its Muscle R2 series—burly Sportster scramblers swathed in carbon fiber and dripping with high-end components and bespoke engineering. But they like to shake things up from time to time, with projects that fall outside their usual domain.
“We do it purely for the challenge, creativity, and enjoyment of building something unique,” says shop boss Chet Perez. “This Honda Grom project was exactly that—a fun, but highly entertaining departure from our usual work, executed with the same attention to detail and standards that define all Cohn Racers builds.”
Cohn kicked things off with a zero-mile 2019-model Honda Grom chassis. “From the start, the goal was to create a compact motorcycle with real race bike character while maintaining balance, rideability, and durability,” Chet explains. “We had seen multiple Grom builds fitted with 250 cc and even larger powerplants, but many of those setups felt excessive for the chassis and often compromised handling, reliability, or overall enjoyment.
“After careful consideration, we determined that a 125 cc two-stroke engine would be the ideal choice. It delivers strong, exciting performance without overpowering the platform, keeping the bike agile, controllable, and genuinely fun to ride.”
The crew sourced an unused 2016-model Yamaha YZ125 engine and modified the chassis to accommodate it… but that was only half the job. “One of the most critical and challenging aspects of the build was addressing vibration,” Chet tells us. “Two-stroke engines are known for harsh vibration, especially when installed in lightweight frames. To solve this properly, we engineered a fully rubber-mounted engine setup.”
“Several custom components were machined specifically for this purpose, allowing the engine to be isolated from the frame while maintaining rigidity and alignment. This solution dramatically reduced vibration and transformed the riding experience, making the bike far more refined and enjoyable than a typical engine swap.”
A peek under the Grom’s fairing reveals much more than a mere engine swap. Cohn threw a smorgasbord of mods at the bike, including a Boyesen Factory Racing clutch cover, a MotoSculpt front sprocket guard, and a Polisport engine protector. A chunky foam filter pokes out on the left-hand side of the drivetrain, with a slightly modified Pro Circuit exhaust system dominating the right and terminating in an Akrapovič muffler under the seat.
“Cooling was also carefully considered,” Chete adds. “The water cooling system was positioned at the front of the motorcycle to take full advantage of direct airflow. This layout works in conjunction with the front air intake, ensuring consistent cooling and reliable performance even during aggressive riding.”
Sticking with the performance theme, Cohn specced the Honda Grom with Öhlins suspension at both ends. A gorgeous aluminum swingarm was installed out back, adding both style and rigidity in spades. The braking system was upgraded with Brembo calipers, larger discs, and custom-made hoses.
The Grom is pictured here with slick tires, but Chete confirms that the compound they use makes them suitable for road use. “From the beginning, this bike was designed to be ridden on the road, not just admired. The stator was modified to generate electrical power, so that it can run a headlight, brake light, turn signals, and a speedometer, making it a true street motorcycle rather than a track-only build.”
Everything is neatly packaged in a full fiberglass body kit, sourced from a specialized manufacturer in Asia. Like the motor, the body is rubber-mounted on custom-made brackets—a detail that called for careful planning and fabrication. “This approach reduces vibration transfer, improves durability, and gives the bike a much more refined feel than most custom builds in this category,” Chete adds.
Painted in traditional HRC racing colors, the Grom has the look of a mini-MotoGP machine. It also sports endless thoughtful little details—from the ceramic wheel bearings to the carbon fiber protectors and accent pieces that are scattered throughout. Custom clip-ons adorn the cockpit, CNC-machined rear-sets from Neverland sit lower down, while an Alcantara-covered seat adds a luxe touch.
Now that Cohn Racers has buttoned up the Grom, they’re ready to sell it and move on to the next project. Unlike their Muscle R2 Sportsters, this is a one-off build that won’t be replicated. And if that doesn’t tempt you to open your wallet, Chete’s glowing review of the hopped-up Grom’s riding characteristics might…
“On the road, the bike is an absolute rocket. The combination of low weight, sharp power delivery, proper suspension, and serious brakes makes it incredibly exciting to ride. It has the raw character of a two-stroke but with a level of refinement that is rarely achieved in custom engine swap projects.”
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