Modern Primitive

Is there a motorcycle manufacturer doing more to stoke the stoke of custom culture than Royal Enfield? The only answer to that question is ‘no’. RE has made the global custom scene a fully integrated part of their marketing strategy. That’s a bone-dry way of saying they sponsor shows and events, and fund custom builds all over the world, then tell people about them. They’re not just dipping their toe in the water, creating a bit of set dressing because it might be trendy, they’re committed. And while there’s overall strategy, each builder is given free reign – no limits or expectations. That freedom has led to RE building a diverse collection of bikes they display at events around the world. In the run up to the 2025 Bike Shed Show there were four brand new factory-sponsored customs being presented, with others being flown in from Japan and the USA to go on display. It’s non-stop.

I’ve been watching RE’s ‘Custom and Motorsport’ department grow for the past few years and wanted a piece of the action. Sideburn has a long history with Royal Enfield. We built a custom 500 Bullet back in 2012 (and put it on the cover of Sideburn 10, with a very young Tim Neave riding it), when Royal Enfield were at the very beginning of their explosion in popularity, and selling roughly 1 million fewer bikes per year than they currently do. No joke. When I saw the new Guerrilla 450 I thought there was a bike we could do something with.

Another piece of the equation is the fact Royal Enfield are not just into custom bikes, they have been investing heavily in amateur and professional flat track since 2019, so the idea was to build a street tracker that was still recognisable as a GRR 450, but classy enough to stand alongside the Enfields built by Sureshot, Sticky’s Speed Shop, Rough Crafts and others.

Making it recognisably GRR involved having Coba Valley fabricate an alloy tank with side profiles and raised spine that echo the shape of the standard tank, while making it narrower than the steel original. A new old stock Harris Performance flush filler was incorporated into the top. Coba Valley also made an alloy tail unit, basing it on the Enfield-designed tail fitted to the Sherpa FT 450 race bike that competes in the DTRA flat track series. Holy Goat Motorcycle Seats upholstered the pad in Alcantara.

The GRR has an asymmetrical swingarm, the right spar having a curve to it, and this led Steelheart Engineering to design and make an industrially-rude billet and alloy tube arm that exaggerated the shape while retaining the standard wheelbase. A Nitron adjustable shock bolted in, using the GRR linkage.

Lowery Racing wheels are used by the Moto Anatomy x Royal Enfield American Flat Track race team, and on the DTRA Sherpa FT, so they were the obvious choice for the street tracker. They’re made by a 20-something married couple, Jeffery and Gab Lowery, in rural Ohio. The front hub was designed and machined to accept the Royal Enfield disc, that is now chomped on by a HEL Performance four-piston superbike caliper. The caliper bolts to GRR forks via a DeftCAD one-off adapter. The forks have been shaved of extraneous protrusions and fitted with SUDO Cycles carbon fork protectors. The rear brake is a monster racing disc mounted on a Lowery Racing quick-detachable centre. A Vortex Racing sprocket is on the other side, with Anlas road legal flat track tyres finishing off the job.

Co-Built made the stainless steel exhaust, just like they did for Bullet we built in 2012 (and a bunch of my bikes in between). They were given free reign and created an avant-garde silencer that compliments the lines of the swingarm it’s tucked under. The header has a few lobster-back sections because it’s a custom bike, so why not, right? Geoff at Co-Built needed a little encouragement to make the pie cuts, because ‘proper’ exhausts have bends and the minimum number of welded joints.

Other details are Renthal flat track bars, Motone Gort tail light, Biltwell grips, CP Racetec hoses, and HEL Performance master cylinders, levers and clutch perch, that are beautifully made in England.

The idea for the geometric paint job has been a part of the project from day one and was laid on by Alex at AK Custom Paint, Essex with the help of Matt from Image Worx. It’s based on the ‘body suit’ tattoo of friend and fellow amateur dirt track racer, Steph Birtwistle. I’ve known Steph since she appeared on the cover of Sideburn 35 in 2018. At the time she was a rider (she arrived at the cover shoot on a road legal enduro bike). After that meeting she started racing, and it was at the British dirt tracks where she met her future husband, Gary Birtwistle. Gary races for the Royal Enfield factory, and also runs the Royal Enfield Slide School in the UK. The pair of them appear in the films we made of this bike, so the tie in seemed ideal. It’s a great pattern without that story, anyway. One thing that might not be obvious from the photos, is that the silver is actually bare alloy, with clear lacquer.

The name of the bike – Modern Primitive – comes from a cult book about tattoos and body modification I saw as an impressionable youth in the late-80s. To me, the name touches upon the tattoo inspiration, but also Royal Enfield’s attitude of building uncomplicated bikes made for riding. The Sherpa motor in the GRR is the company’s first liquid-cooled production engine. As fans of street trackers and flat track racing at is most fundamental, that simplicity really appeals to us at Sideburn.