Open-class two-strokes are a rarity nowadays, with Japanese manufacturers halting their production in the early 2000s, rendering parts for these iconic machines scarce.
Nevertheless, the aftermarket industry is steadfastly refusing to let the 500cc sector fade into oblivion. Companies like BRC Racing and mXrevival are injecting a substantial dose of vitality into it. The GasGas MC500 stands as a testament to this resurgence.
It’s always exciting to witness companies go the extra mile with customization to breathe new life into a build. This particular project began with the acquisition of a slightly used 2023 GasGas MC250 from Carl’s Cycle Sales in Idaho.
While the machine was in good condition overall, Charles at mXrevival harbored grand ambitions for it from the outset—doubling its displacement, revamping its appearance entirely, and enhancing its performance to unmatched levels. Ambitious goals indeed.
Doubling the displacement might sound outlandish, but it turned out to be a relatively straightforward task for this project, thanks to the assistance of Riley and the team at BRC Racing in Canada.
BRC’s 500cc engine conversion is engineered to seamlessly integrate into the last-generation KTM, Husqvarna, and GasGas steel frames with minimal modifications.
Certain internal and electrical components were sourced from the MC250 engine, with additional electric starter parts sourced from KTM due to the kickstart-only nature of the donor engine. Tony Jeske from Elite Moto Factory oversaw the assembly of the BRC engine kit and the transfer of necessary parts from the MC250 engine.
In addition to the significant power boost, it made sense to upgrade the suspension, brakes, and drive. Brandon at AHM Factory Services took charge of the suspension requirements for the Helfyre project.
AHM customized the stock fork tubes and shock body with a striking gold finish, while also applying DLC coating to all lower shafts. Notably, AHM carried out a comprehensive conversion of the AER air fork, outfitting it with complete Yamaha KYB/SSS spring components.
A 500cc GasGas motocross bike seemed like an impossibility, but Charles from mXrevival and Riley at BRC Racing Canada confidently declared otherwise. And they were proven right. Just when we thought we’d seen it all, this project emerged, surprising and delighting us with its finished form.
What’s truly remarkable about the BRC Racing engine conversion is that it not only doubles the engine displacement but also retains a counterbalanced, exhaust-valve-equipped engine while adding electric start to the previously kick-only GasGas model.
The BRC Racing engine kit stands out for its impressive fitment and utilization of every inch of available space. Overall, the performance of the BRC engine is highly commendable, delivering tractable power and eliciting smiles, particularly when short-shifting through the midrange powerband.
Although tuning the Lectron metering rod-style carburetor proved to be a challenge, the suspension setup executed by Brandon and his team at AHM Factory Service was nothing short of impeccable. Not only does it boast a visually stunning factory look courtesy of specialty coatings, but it also performs flawlessly.
Collaborating with Charles and the various companies involved in his builds has been a pleasure, and we eagerly anticipate future projects. Stay tuned for what lies ahead; there’s certainly more excitement on the horizon.