Here at BSN, we’re a touch ambivalent about the current retro custom bike scene. Yes, we’re all for people getting into bikes, and modifying machinery to their own tastes. We’re not even that bothered about beards and top-knots (sort of). But the bike themselves are often the exact opposite of why we got into bikes: many of them are slow, heavy, ill-handling triumphs of form over function. Which we do not like at all. Oh no.

But this new bike from British firm Spirit, dubbed the GP-Sport – promises to change all that. Because it marries up the best of the custom scene – hand-built stuff, high-quality materials, innovative design – with a lovely set of good old-fashioned performance stats. Based on the Triumph 675 Daytona motor, Spirit has produced a 180bhp 750cc triple, bolted it into a hand-brazed adjustable frame, added the best of British suspension from K-Tech, and sweet PFM brakes. Best of all, the whole thing weighs in at a claimed 145kg wet for the top-spec ‘R’ version. Eek! They’re even offering a naked GP-Street version too.

Using the Triumph triple engine as a base is a clever move – the three-cylinder motor has been around for years now, and is a sorted design. Tony Scott has been tuning and upgrading them for racing for as long as we can remember, so he knows what works on them and what goes wrong. Taking the capacity out to 750cc is a master-stroke(!) – and we’re not totally clear how they’ve done it. The bore is 76mm – same as the current 675 Daytona. But the stroke is up from 49.6mm to 55mm. Now, life would be very simple if Triumph’s 800 triple crank had that stroke and could be swapped over. But its stroke is 61.9mm, so they’ve not done that. We’ll be pushing to find out just what witchcraft they HAVE done…

Engine internals aside, the new bike has a high-compression 13.8:1 cylinder head, and uses a full Motec M130 ECU. There’s a Bosch electronic slipper clutch, which is intriguing, a full titanium hand-made T3 exhaust system, race kit harness, and a sweet 428 low-friction final drive chain, which we love. It all adds up to a fruity 180bhp@14,200rpm, at the tyre on the ‘R’ versions, and 156bhp on the base bikes.

Those engine specs are a delight – but the chassis will beguile just as much. First up is the sweet brazed steel tube frame. Brazing is an old-school technique to join metal. Unlike welding, it doesn’t melt the base metal together, rather it ‘glues’ the parts together with a different, molten, metal, that melts at a lower temperature than the base material. That means less heat and less distortion, at the cost of more time and labour costs. It’s a far more involved technique, that needs great skill to do properly. It does, however, look awesome, the brass-coloured braze fillets highlighting each joint in the trellis design. That brushed cast aluminium swingarm (made by Harris) is also very easy on the eye.

Spirit has kept up the British theme with the suspension, fitting K-Tech front forks and rear shock. On all versions of the bike, you get the KTR 2 fork, which is normally seen on the likes of Padgett’s TT race bikes, and a 35DDS Pro rear shock, both fully adjustable.

Now the bad news, sort of. A spec like that above doesn’t come cheap of course, and the GP-Sport ‘R’ will set you back £65,000. The base version is a bit cheaper, but still £45k. Surprisingly, the naked bike costs the same – the Street ‘R’ actually lists at £70,000 (making it the most expensive naked bike we can think of…), and the base Street is again £45k. Not at all a cheap option – and the ‘R’ is about the same price as Ducati’s new Superleggera 1299. But it’s also limited to just 50 machines, so you’re even less likely to come across one at the lights on your wet Monday morning commute…

Spirit Motorcycles is a tie up between two top UK bike-building firms – Tony Scott’s T3 Racing and custom specialists Spirit of the Seventies. T3 knows all there is to know about the 675 Daytona, having basically run an entire cottage industry around racing it in the UK. Meanwhile, Spirit of the Seventies has made a series of achingly-pretty custom bikes in recent years, that also offered much more in the way of performance. Both firms are based in Kent, and their new venture is also located in the Garden of England.

The firm is launching the new GP-Sport and Street at a plush event at the Bike Shed in London tonight. We’ll be finding out more about the 750cc engine, the electronic riding aids, carbon bodywork, and much more, from the Spirit bosses. Check back for more as we get it…