Blown away by the ultimate NSR rep

Published: 27 September 2015

Stunning build quality, brakes that defy belief and the world’s coolest wife have all merged to make James Mansfield’s Honda NSR500 replica the best special we’ve ever ridden. Seriously… 

t’s all our fault. James Mansfield probably wouldn’t be the owner of the world’s best Honda NSR500 replica had PS not featured the Spondon Suzuki RG500s of Nick Tilley and Robert Johnson back in Issue 10 (August 2011). Those bespoke, Darren Lane-built GP reps set James on a path that eventually led to the creation of this mind-bendingly gorgeous Doohan rep 500. 

“Seeing those Schwantz-rep Spondons was a real light bulb moment for me,” explains ex-pat James, now based in New York. “It was like, ‘That’s what I want’".

Then fate played a blinder. James was Stateside popping the question to the lady in his life, Julie. Luckily she said “yes”. Julie then proved that she is possibly the finest female ever to walk this earth when she presented James with a picture of Mick Doohan’s NSR500 GP bike saying, “And for a wedding present, how about I get one of these built for you?” No prizes for guessing his answer…

Despite living in New York, James knew he wanted a bike built in the UK. “Cost was a big factor,” he explains. “Getting a bike like this built in the States would cost four times what it does in the UK. Secondly, building a bike like this that actually works requires really specialist skills – I’ll hold my hands up and admit I’m not that man.”



That’s not to say James wasn’t hands-on with the build. “I was very involved in the whole process; sourcing parts and finding people to supply components and do jobs, but I leave guys to it once I’ve made the choice. I own a construction company so project management is my business. It doesn’t guarantee success but it gives a sense of how much rope to give someone, how often to check in and what milestones to set to determine if they need to be cut loose.”

Doohan it & Doohan it well

The basis of James’s NSR replica is its 2moto chassis – expertly fabricated by Barry Dawson, 2moto’s chosen fabricator. The powerplant is far from ordinary. With no viable Honda unit available, and James knowing that an RG500 mill has a far greater potential for reliable tuning than an RD-V4, a Suzuki RG500 lump was the obvious choice for a project focused on creating the ultimate two-stroke GP replica. With the square-four at its heart, the chassis had to be tweaked to accept the physically smaller Suzuki lump, and a one-off lower cradle devised to provide lower engine mounting points.

“All the parts had to be sourced. I said I needed to find an RG motor, but Barry said there was no need. He already had one on the bench that’d been bored and tuned to make 120bhp in full race trim.” Not only that, it came with a bespoke close-ratio gearbox and dry clutch – one of only a handful that Nova had made for Padgetts. With that in place and a target wet-weight of just over 130kgs, the recipe for outrageous performance was there.

The swingarm is from an R6; it works, fits the dimensions and is considerably cheaper than fabricating one from scratch. Its movemement is controlled by an Öhlins TTX shock – a fully-adjustable thing of beauty that has been set up at the factory for the bike and James’s weight. Not to be outdone, the front wears Öhlins FGRT200 forks. They’re the highest spec units the firm make before you get to GP-grade forks that require ludicrously regular technician-assisted maintenance. But why not go for Showa, as per Doohan’s bike?

MAR 2015 ON THE CASE

A set of slave RG cases acted as part of the jig to create the 2moto frame, made from 3mm 5083 aluminium sheet and billet.

MAR 2015  CUT IT OUT

The business end is neatly tucked away under an aluminium cover, which Barry made first as a cardboard template.

 

MAR 2015  THE REAL DEAL

The bodywork doesn’t just look like Mick D’s – it’s from the very same HRC moulds. Made in carbon by CTech Composites.

 

APR 2015  GET IN LINE

Rapier Paintwork lined up the Rothmans paint to run seemlessly from seat unit to fairing. Their prep work is meticulous.

 

APR 2015  FULL COLOUR

A whole lot of love and attention went into the paint. It’s all paint – no stickers. All that red you see is for just one single pinstripe.

 

APR 2015  BILLET BEAUTY

Buying yokes off the shelf would never do for such a build. Like the swingarm pivots and headstock, it’s milled from billet.

APR 2015  RACE READY

Stage 3 RG500 motor with Nova ’box and dry clutch. Makes 100bhp in road trim; good for 120bhp with saucy disc valves…

MAY 2015  BACK (END) IN THE GAME

The swingarm may be Yam R6, but all the linkages and shock mounts are bespoke to match the dimensions set out by 2moto’s Felix Hirzel, who designed the chassis. Note the mount, behind the swingarm pivot, for the adjustable 2moto footrests.

MAY 2015  IT’S A COVER UP

Protecting finished components, such as these gorgeous one-off silencers, is one of the tricks of bike building. Note LED light.

MAY 2015  CALL IN THE PLUMBER

How you fit the ancillaries, plumbing and wiring is what can often make or break a special. Note how neatly mounted – and accessible – the coils are just behind the headstock. PS friend and regular contributor Rupert Paul made the loom from scratch.

“Finding period Showa stuff would be nigh-on impossible,” explains James. “Plus it’d be old and need rebuilding, and even when that’s done it wouldn’t be as good as the Öhlins. I want the bike to ride as well as it can – it’s not just about looks. Price was another factor. I could have bought used forks. That would have cost about $1800 by the time I’d had them rebuilt. These are brand new, set-up to my spec at the factory and they’re only $500 more.”

It sits on feather-light carbon fibre BST rims that quicken steering and turn-in, as well as keep the bike’s weight on target. If you look carefully you can still see the carbon weave through the deliberately unpainted HRC logos on both wheels.

Braking is as good as it gets. Brembo monobloc P4 calipers controlled by a matching Brembo mastercylinder and quick release Hel lines grip EBC floating discs. GP carbon rotors can’t get up to temperature on the road, but with the performance this set-up offers they’re simply not needed. 


What makes or breaks any replica is its closeness in appearance to the original. In the case of James’s NSR you really do need a double-take when you first see it. Could that actually be Doohan’s bike? 

“The first rule of a replica is that the silhouette must be right,” says James. “If it’s not, the bike will never look right. I spent ages researching fairings and eventually found Russel Lowe at Bike Styles UK, who had the original HRC moulds from Doohan’s 1998 bike. He rescued them after the team threw them in a skip at the German GP. He used his old MotoGP contacts to help me get CTech Composites in High Wycombe to make carbon fibre bodywork from the moulds.”


But all that would be for nothing if the fuel tank looked out of place. It was made from scratch by Neil Martin of CC Engineering in Hull. “It’s real, old fashioned artisan metalwork,” says James. “There’s no filler whatsoever in that tank. He started with a block of wood, then hand-beat and English-wheeled the tank from sheet ally.”

The tank perfectly encapsulates the level of detail and excellence that has been lovingly put into this build. From the adjustable milled billet footrests and hangers, handmade expansion chambers, one-off subframe, simple yet elegant choke levers (one for each pair of carbs) and specially designed and machined yokes, the whole bike screams ‘best of’.

Being a Doohan replica, James’s bike could have been finished in any of three paintjobs: Rothmans, HRC or Repsol. For its owner, however, there was only ever one choice. “I built a Wayne Gardner Tamiya model when I was 16 and I thought it was the best bike I’d ever seen – the tobacco advertising in the ’80s created some epic looking bikes.”

The paint was applied by Rapier Paintwork in Hull, and the finish is astonishing. They’re not graphics – it’s all paint so lustrous and deep you feel like you could dive in. It looks magnificent from any distance, but close up it’s another level. The black pinstriping and numbers reveal naked carbon fibre; it’s so subtle you miss it at first. And the Rothmans blue is pearlesant, coming alive in sunlight.

You’ll have gathered by now that James is a very particular fella. “I put a couple of hours every day for 18 months into this bike; making calls, doing research. The build process is a constant buzz that gains momentum, followed by massive disappointments when you realise something you’re building is never going to work. 

“When I saw the bike complete for the first time I was very anxious. I just didn’t know if it was going to be a massive disappointment to ride. I’m a rider, not a polisher, so it has to work or it would be pointless.

So what were James’s first impressions?

“Astonishing. The bike blew me away. It rides and handles better than my NSR250 (MC28), and that’s one of the sweetest bikes I’ve ridden. This has got twice the power, too. Amazing.”

That Barry Dawson built this whole bike in such a tight timescale – just seven months from start to finish – makes the whole project even more impressive. But like all specials, it’s still not quite finished. To further create the illusion of an HRC 500 on the road, it will suck air through carbon fibre airboxes mounted either side of the motor. James already has a man in mind who works in F1 to create these finishing touches, but he’s keeping tight-lipped about his identity…

The engineering, design, build quality, execution and sheer gorgeousness of James’s NSR make it the finest of its kind in the world. I’ve not seen better, and I doubt I ever will. But does it ride as well as it looks?

Riding it

Let’s cut to the chase. This is the best special I’ve ridden. Ever. Just look at the numbers: 100bhp, 132 kilos fully gassed and the chassis geometry of a GP bike – a recipe for explosive lunacy if ever there was. To give it some context, that’s the power of a decent 600 but with 50 kilos less to lug about.

If you’ve ever ridden an NSR250R MC21/28, sitting astride this Rothmans rep would be familiar. The riding position is business-like, yet spacious enough to be comfortable. The handmade tank is slimmer than the modified NC30 part on James’s YZR, allowing me maximum tuck behind the low screen. The billet ’pegs are high enough to never touch down, but not so high that they cramp my legs, and the forward sloping seat ensures I’m tipped over the bike’s tour de force – its front end (more about that later).

But let’s start with the engine. There’s no kickstart; the Nova gearbox has no fitment for one. There’s no fancy electric start either. Just like the bike it’s aping, James’s Rothmans rep needs a push and bump to fire into life. That could be a pain, but it’s not. Once acclimatised, I’m able to bump the square-four into action with just two forward steps and a dump of the clutch. 

Even at idle this one-off stroker radiates malevolence. The quartet of spannies cackle away menacingly, and in the background the dry clutch clatters like a rattlesnake warning of imminent attack. First gear is tall – it’s a close-ratio race ’box after all, so the motor needs a fistful of revs and a measured slip of the clutch to get off the line with any panache. 

We’re on the Isle of Man, and it’s TT time. The Mountain Course is awash with halfwit heroes on S1000RRs trying to be Michael D.

Neither James nor I fancy placing 40 grand’s worth of hand-built special in the middle of that, so we head for quieter roads where we can stretch the NSR’s legs in peace. The road of choice is the A36 between Foxdale and Port Erin. Up to the Dalby turn-off its surface is beautifully smooth, before the road returns to type and bumps become the norm. 

Unlike the bike. It’s anything but normal. Between the bends I’m throwing as many gears at the tuned 570cc motor as my left foot can snick. The power delivery isn’t peaky as I’d anticipated – there’s power everywhere, the presence of which is made all the more obvious by the bike’s lack of weight. From 8000rpm onwards, however, it goes berserk, lifting the front wheel in the first three gears if you’re aggressive enough on the gas. Everything happens so rapidly that my senses are struggling to keep up. 

What I’d previously considered to be long straights become short shocks of arm-tugging violence. I’ve barely got a split-second to glance down at the digital Translogic dashboard. Even when I manage to steal a look, the tacho blobs and digital numbers are changing so rapidly that I’m unable to glean anything of importance. There is no rest.

Then, as quickly as I’ve left the last, another corner is on top of me. My brain is telling me we’re going 20mph too quick. I brush the front brake lever with my index finger and the speed is cut away as if by a knife. The lightest of inputs to the ’bars and ’pegs lean us into the turn and… bam, it’s all over – corner gone, and we’re on the next straight. 

I’ve never experienced brakes or suspension this good. The sheer power of the Brembo radial set-up takes my breath away. T wo fingers on the lever and it’ll stoppie from 80mph, as James proves on the return from yet another fuel stop (we’re doing sub-10 miles to the gallon). The control and quality of the suspension, too, is such that my brain simply cannot usefully compute or use the amount of information it’s feeding back to me. 

Even on the undulating section of the A36 down to Port Erin, the NSR’s manners are impeccable. This flies in the face of everything I’ve ever experienced of light bikes on rough roads. I brace myself for a bucking bronco ride, but it never comes. The NSR rides the bumps on a cushion of Öhlins damping that instead demands more throttle and more speed. 

After 15 minutes I’m done. My gloves are soaked with sweat and my brain has crashed like a broken computer. I’m not even sure what just happened. James set out to build the ultimate NSR500 replica. It’s been a steep learning curve and, yes, there has been little change from 40 large, but it’s not hyperbole when I say that this is, without doubt, the ultimate NSR rep. Damn it, it’s the best two-stroke road bike ever, and far and away the finest special I have ever ridden. A job well done. 

SPECIFICATION

ENGINE

Type liquid-cooled, disc-valve, two-stroke square-four with AEC
Capacity 572cc
Bore x stroke 60mm x 50.6mm
Compression ratio 7:1
Ignition Gnitech
Carburation 4 x 35mm Mikuni TMX flatslide

TRANSMISSION

Primary/final drive gear/chain
Clutch dry/multiplate, Nova
Gearbox 6-speed close-ratio Nova

CHASSIS

Frame aluminium beam, 2Moto, Yamaha R6 swingarm
Front suspension Öhlins FGRT200 usd forks, fully adjustable
Rear suspension Öhlins TTX shock, fully adj
Front brake 2 x 320mm EBC discs, 4-pot Brembo monobloc P4 calipers
Rear brake 1 x 220mm disc, 2-pot Brembo caliper
Wheels 5-spoke BST carbon fibre
Front tyre 120/70 ZR17 Pirelli Diablo Supercorsa
Rear tyre 180/55 ZR17 Pirelli Diablo Supercorsa

DIMENSIONS

Wet weight 132kg (291lb)
Wheelbase 1390mm (54.7in)
Seat height 780mm (30.7in)
Fuel capacity 18 litres (3 gals)

PERFORMANCE

Top speed 160mph (est)
Power 100bhp@11,000rpm
Torque 54lb.ft@10,000rpm
Fuel consumption sub-20mpg

Thanks to

Julie Mansfield James’s wife who paid for it!
Peter Mansfield for untold trips between York and Hull with bikes and bits
Felix Hirzel 2moto, 2moto.co.uk
Barry Dawson Blue Haze Engineering, 07754 191773
Clive White at Rapier Paintwork rapierpaintwork.co.uk, 01482 212 690
Dave Reynolds for the ignition set up, 07740 479050
Rupe’s Rewires rupesrewires.com, 01832 270195/07736 212652
Robbie Sylvester and Slick Bass for finishing off the set-up and jetting for the TT
Dave Hewitt, Mick Ellis and James Garritt for helping out in the IOM