Sideburn x Royal Enfield Films

As part of the Royal Enfield Guerrilla project we made a couple of films and a special edition magazine. The films featured Steph Bolam and her husband, Gary Birtwistle, and were made by our long-time collaborator Black Dots Video.

Film one above, film two below.

The vintage Lewis Leathers jacket that features in film two was hand-painted by Cobra Signs.

We filmed at Iwade Speedway Track, who couldn't have been more accommodating. You should go race there, or do a Royal Enfield Slide School.

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.

Words: Gary Inman

Photos: Craig Stuart / @scrambler_ams

Grantham Honda GB350

Our mate Jim is manager at Grantham Honda and built this neat street tracker for a European Honda dealer competition. Vote for it here

Here are Jim's words on the bike.

Based on a GB350, this bike has been built by the team at Grantham Honda to be taken to Wheels and Waves in Biarritz this week as part of the Honda Custom build competition where bike builders from across Europe compete for your vote.

‘’We went for a flat track inspired build, the brief was fairly free and easy from Honda, as a show bike it didn’t even need to run… but we’re not really interested in making something that couldn’t be raced or ridden to the pub, I don’t see the point. Being a new-to-market bike in the UK there aren’t many off-the-peg parts available for this model, so we needed to call on some good people.

Most things start with an exhaust. Apart from a bolt-on Yoshi silencer, there wasn’t anything available, and we figured everyone would fit this one. I called an old friend for a very special favour – a full titanium system from the legendary Racefit, built in the UK by hand. Proper stuff. Proper one-off. Proper noise.

For the seat unit and fork guards we gave A16 Racing a call, just up the road. It’s nice to use local people when possible and their fibreglass is spot on. I’ve seen a lot over the years, but this is good stuff.

The paint was done by a good friend Paul at Barkston Refinishing Limited, two mins down the road, great bloke, stopped an Air-cooled 911 respray to get stuck into this, he ‘gets’ bikes…that’s important. We came up with a modern take on the CB schemes from the late 70’s. And stole my race number for the tail and number board…

We had a couple (underestimate) of problems to overcome… rearsets… I wanted billet machined rearsets… nice ones. Proper ones, CNC’d, one-off stuff. And some trick triple claps, shiny, billet aluminium, CNC’d, cool. Best ring DEFTCAD engineering… Tom was as excited as me to get cracking and come out to the dealership with a 3D scanner to start the design work.. Incredible stuff. Couple of weeks later, there you have it! Unreal! Tom said they fitted so nicely he’s thinking of putting them into full production! Watch this space…

Wheels were tricky, again we had to go custom, we managed to get a set of not-yet-available hubs from Rally Raid Products and sent them straight to SMPro Wheels to be laced to 19 inch rims. Shod with 19inch Dunlop DT3s it transformed the stance of the bike immediately.

Brakes.. I know Flat Track bikes don’t have a front brake… we all know that. But just like leaving the rear brake light in place, we wanted the bike actually to be able to be ridden and enjoyed. We phoned helperformance.com for a master cylinder and custom brake lines after removing the ABS system, and ended up with a thumb brake and Hel clutch perch as well… Do we need it… no.… is it cool…. yes. Best bit of all, proper UK made stuff. Nice.

Why the bloody great big K&N sticking out of the side…. Because it’s cool. When I was a nipper, big K&Ns were cool, and it took me back to my youth just looking at it. And the induction noise is something else.

At the last minute we decide the engine looked a little ‘plain’ so the guys at Motone Customs came up trumps with a pair of engine cases, they’re made for CB350s but fit the GB perfectly and really look the part, top tip. A quick bolt on for your GB that really changes the look. Unfortunately the pics we took were taken before the covers arrived but check out the link from Honda for the latest pics.

Nearly all the parts were made in the East midlands, and with the exception of the K&N, all the parts were made in the UK. By proper people, doing a proper job.

There’s a lot more that went into this but they’re the ‘highlights’… Enjoy the pics.’’

It would mean the world to me and the team at Grantham if you could take two seconds to VOTE for our bike build.