A decade after Honda had revolutionised the motorcycle industry with the introduction of their four-cylinder CB750, they had done just about all they could with the platform. Competitors were now producing sports bikes of a litre or more capacity, and the Japanese manufacturer decided it was time to join the party. Enter the CB900 Bol d’Or, not only was it named after a famous endurance race, but the engine was derived from the factory race program too. And what an engine it remains to this day, but the supporting infrastructure hasn’t held up so well. So, to craft a true racer for the road, Asen Zahariev of Bulgaria’s Tossa R has thrown all but the kitchen sink at this bike, creating a resto-mod rocket with pimped-out good looks.

The arms race of the Cold War was still raging in 1979, and it was no different on the showroom floor, as the no replacement for displacement motto, saw manufacturers upping the capacity of their sports-orientated motorcycles. Honda had always preferred high-revving multi-cylinder machines, but eventually, they had to follow the pack if they were to stay competitive. And if you want more inches, why not stroke it, which is exactly what Honda did. Taking the basic infrastructure of the CB750 and increasing the capacity to 900cc, while adopting their race program’s camshafts for the project too.

The bike that Asen started this build with also came fitted with the factory suspension, featuring TRAC and other advanced systems for the time. But brakes and suspension have come a long way in the last four decades, and one thing Tossa R loves to do is combine the character-filled engines of the past, with a supporting package that lets you use the horsepower to its full potential. To do the job properly, the bike was pulled down to a bare frame and with no intention to keep the standard rear end, the subframe was cut off to the centre post.

Next, a new swingarm was chosen from a CBR600, with the box section unit replacing the twin-shock steel tube setup that came from the factory. To make this work, the bearings are replaced at the pivot point and new spacers get the alignment spot on. Now to make the frame match and a shock mount has been fabricated and heavily braced for the new mono-style conversion. A new subframe has been built too, drastically shorter than the factory offering and crafted to provide for some seriously aggressive lines. Finishing out the conversion, a single shock goes in, with the spring painted in gold to match the remote res.

The front end would lose the air-assisted folks, but it gains a big win in the form of a full conversion to a modern Kawasaki setup. Taken from Honda’s main rival, the forks and trees are from a ZX6-R and provide a massive improvement in handling, with the supersport also donating its 17-inch wheels which are now fitted with modern rubber. The braking package is all new too, with a set of big wave pattern rotors clamped by four-piston calipers for the front, and the rear benefitting from the fitment of a single drilled rotor and new master cylinder and caliper combination.

Now with the bike rolling, Asen could give the CB the signature Tossa R style, with bold paint and a landscape dominated by the fuel tank. The rear mount of which has been modified so that the unmistakable lines of the tank sit parallel to the ground, a drastic improvement over the stock appearance which has the metal drooping at the rear. A small tail section has then been handcrafted, with the lines from the top and rear section of the tank, replicated in the new metal. The paintwork is stunning, with the popular Audi-inspired grey brought to life with gold logos and accents.

This look is then extended across the bike with the calipers wearing the same gold finish and the forks have come dressed for the show. Even the custom-built rearsets get the treatment, with the knurled surfaces finished in the gold look and the heel guards anodised to suit. Those foot controls form the first step in creating a very sporty riding position, with the bars now low slung clip-ons, the sit up and beg riding position now a thing of the past. The new bars sport a great combination of beautifully refurbished switch gear and the very best levers from Brembo, matched to an Italian master cylinder.

LED lighting adds a modern touch throughout and to clean up the front end, a small Koso digital dash has been employed. Finally, Asen could turn his attention to the famous four-cylinder and he’s ensured it’s looking its absolute best, with a fresh coat of heat-proof black paint and some polishing on the covers and fins. The stock carbs are totally rebuilt to flow more fuel and air, with the aid of a set of pod filters across the bank. While that exhaust system is all about the sound, a pair of two-into-one header pipes merging back into twin reverse cone mufflers which we’ve heard at full noise and are music to our ears. The finished product is flawless from tip to tail and Tossa R has given a new race-inspired life to another classic bike worthy of such tender love and care.  

[ Tossa R ]