Three Harley-Davidson motorcycles pushing a century old — a 1924 Model JD, a 1927 Model JD, and a 1921 Model FD — just got a second life that their original engineers couldn't have imagined. Oxford-based EV conversion firm Electrogenic has transformed all three into either plug-in hybrids or a full EV, and the conversion kit that makes it possible is available to order right now.The builds premiered in episode 4 of Jason Momoa's documentary series On The Roam Season 2, airing on HBO Max and Discovery+. Momoa, who previously worked with Electrogenic to electrify a 1929 Rolls-Royce Phantom II, brought the century-old Harleys to the Oxford shop as the next challenge — and by his own account, the results exceeded what he expected. How Electrogenic Married 100-Year-Old Engineering With A Modern EV Powertrain ElectrogenicThe core of the conversion is an 11kW Maeving hub motor built directly into the rear wheel, producing 260Nm (190 lb-ft) of torque — nearly four times the 50 lb-ft the original 74-cubic-inch twin-cylinder engines made at the crank. Electrogenic CEO Steve Drummond noted that Maeving is the only manufacturer in the world producing a hub motor powerful enough for the application, and sourcing those units required a direct arrangement with the UK-based company.The 2.7kWh battery packs live in custom panniers sized to match period-correct originals — just a touch deeper to accommodate the cells. They're removable for charging separately or can charge on-bike via a standard AC wall outlet in roughly 2.5 hours. The right-hand pannier still leaves room for a packed lunch, which feels very on-brand for a build designed around off-grid riding.Critically, nothing on the original motorcycles was cut, drilled, or welded. Every conversion is fully reversible — a non-negotiable for Electrogenic across all its builds, and especially important here given the historical significance of machines this old. Three Modes, One Switch — And No More Kick-Starter Mishaps ElectrogenicThe two JD hybrids offer three riding modes selectable on the fly: petrol-only, electric-only, or combined power with both systems running together. Electric-only range exceeds 50 miles, with the petrol engine extending that further whenever the rider wants it. Drummond described the combined-power pull in second gear as "addictive" — 260Nm of instant hub-motor torque layered on top of a vintage V-twin is a combination nobody has ridden before.The 1921 Model FD tells a different story. Its engine was seized beyond any practical repair, which made the full-EV treatment the only path forward. It now runs entirely on the Maeving hub motor setup — a bike that was functionally dead is rideable again.For all three machines, the hub motor doubles as an electric starter for the petrol engines on the hybrids, eliminating the kick-starter entirely. That's not a small quality-of-life upgrade on bikes from this era; century-old kick-starters were genuinely dangerous, and the original machines also had no front brakes — stopping relied on a band-style rear brake and engine compression alone. Electrogenic added a modern disc brake to the rear wheel on each bike, a change that quietly makes these machines far safer to actually ride in traffic.“I’m always excited about what’s happening with technology and how we move through this world. So that’s the motivation (for these projects). I live a life that’s kind of off the grid, and I love being outdoors… I want to be able to stay outdoors and try to do something in a more sustainable way.”Jason MomoaMomoa's reaction to the finished bikes is worth quoting at length, because it captures something the spec sheet can't fully convey. "I've ridden on an e-bike before, I've ridden on e-bicycles, I've ridden on e-motorcycles," he said, "but the idea of riding on an old (electrified) bike, it was just unlike anything I've experienced. I can have a full conversation with my friend, just going through the mountains… cruising on this old 1920s bike, and totally feeling it's a 1920s bike. It's just a really beautiful experience."The mode-switching capability is central to that experience. Want the exhaust note and the mechanical character? Run petrol. Want to ghost through a forest trail with your daughter? Flip to electric. Momoa put it simply: "If I want to hear the sound I can, and if not I can just flip it over." For a machine built in 1924, that flexibility is remarkable. The Kit Is Available Now — Here's What That Actually Means ElectrogenicUnlike most celebrity builds that exist as one-offs behind velvet ropes, Electrogenic's Harley hybrid conversion is a purchasable product. The drop-in kit is listed on Electrogenic's website and available for worldwide shipping through the company's partner installer network, which spans Europe, North America, Africa, and Asia Pacific. The kit is designed to work with period Harley-Davidson models compatible with the rear-wheel hub motor fitment — prospective buyers should contact Electrogenic directly to confirm fitment for a specific machine.For gearheads sitting on a barn-find JD or a seized flathead that hasn't run in decades, this changes the calculus considerably. A bike that can't be practically restored to running condition on its original engine now has a viable path back to the road — and one that doesn't compromise the original hardware in the process.Electrogenic's previous work with Momoa — the 1929 Rolls-Royce Phantom II conversion, still described as the most ambitious EV conversion completed globally — established what the Oxford firm is capable of. The Harley hybrid kit is something different: proof that the technology has matured enough to package into a product anyone can order. For collectors with century-old iron gathering dust, that's worth paying attention to.