Fred Bertrand’s supercharged SR400 is an engineering masterpiece and has close links to MotoGP via the bloke on the right – Valentino Rossi ‘s technician
We all know Yard Built as Yamaha’s clever way of promoting their Sport Heritage range by getting top custom builders to show what’s possible with ingenuity, engineering skills and a flair for design. But it seems perverse to suggest that Krugger’s super clean, supercharged SR400 Yamaha was built in a yard. It looks more like it’s been created in a MotoGP race shop, where the work surfaces are clean enough to eat off and technicians use banks of computers to eek out that last split second of lap time. The MotoGP analogy isn’t too wide of the mark because when Fred Bertrand, the man behind Krugger Motorcycles, agreed to collaborate with Yamaha on a Yard Built project, he took inspiration from close friend and fellow Belgian Bernard Ansiau, who happens to be a MotoGP mechanic for some bloke called Valentino Rossi.
Fred’s Krugger Motorcycles is a Belgian-based custom shop with a glittering array of award-winning builds, while Bernard’s CV is littered with MotoGP legends, having previously prepared the racing machines for Yamaha greats such as Wayne Rainey, Kenny Roberts, Randy Mamola and Norick Abe. Fred and Bernard agreed to use the humble Yamaha SR400 to bring alive the racing spirit of the 1970s in a tribute to the Yamaha TZ machines and also to celebrate Bernard’s career. Compared to modern day ‘plug and play’ MotoGP, the ’70s spirit was a very different – a time when technicians ported cylinders, changed carb jets and welded frames – much more in keeping with the custom builder of today. As you might expect from a build inspired by the pinnacle of MotoGP, Fred has given this little SR400 engine (97mm bore x 62.7mm stroke for 399cc) some serious work.
The most noticeable difference is the beautiful Aisin 300 supercharger with its custom- built plenum chamber. Fred says: “After I built NURBS (the Tron- like six-cylinder BMW K1600 projectile from 2014) I’d had enough of big bikes for a while. I was a little bit bored with them and I love the smaller bikes so I decided to embark on this project, based on the SR400. “It was easy enough to fit the supercharger into the space on the SR but the challenge was to machine everything to be able to run the belt drive for the supercharger with the original rotor/magneto. The engine runs a slightly lower compression of 8:1 (compared to the stock 8.5:1) and I had to build a plenum chamber that’s 250 percent of the original engine capacity (ie, one litre). The supercharger works at three times the speed of the engine crankshaft and delivers 9.95psi of boost.”
There’s a hand-built, one-off stainless steel, swept back exhaust system, complemented by an S&S 48mm carb in place of the fuel injection system. “I did the initial calculations to set the system up and then it was a question of fine-tuning it. It makes a reliable 45bhp (compared to the stock 27bhp). The engine never stops accelerating. It’s really nice to ride,” says Fred. The beautifully polished forks, sitting in equally polished stock yokes, have been lowered and balanced with a set of Fox shocks at the rear. Wire wheels are shod with a set of Dunlop K81s, inspired by the first tyre to lap the Isle of Man TT course at over 100mph.
Fred’s obsession is evident all around the SR400. Switches and grips sit behind a tiny custom cowl at the front above a modified top triple clamp and custom handlebars. The single disc front brake (and clutch) are by Beringer, adding some power over stock to match the supercharged 400 motor. The standard SR400 fuel tank has been kept, but reworked narrower and longer with the filler cap relocated centrally. It now resembles an OW31 TZ750 gas tank, while a custom tail unit hides all the electrical components. Fred adds: “The standard frame has an oil-carrying single tube spine, but I’ve added frame rails to run along the base of the tank and modified the subframe to suit the seat.”
A stunning interpretation of the Yamaha speedblock colours in blue and white (tipping a nod to the ’70s Gauloises livery of the French Sonauto Yamaha importer) completes the colour scheme, with the names of all the riders in Bernard’s racing career written into the design. By why not the more famous yellow and black Yamaha livery, or even the red and white? “Because this is Bernard’s original old colours,” says Fred. “The livery was his choice.” “This really is a unique piece of art,” said Yamaha’s Marketing Coordinator Cristian Barelli. “I think it’s impossible to have a custom machine that lives and breathes our racing history better than this.”