BSD Honda Hornet CB600F

Dymags, AP Racing, PFM, Öhlins...
sounds like a million-dollar Grand Prix bike? No.

BSD Honda Hornet front three quarter view

SPECIFICATIONS..

Engine : 1999 Honda Hornet. 1997 CBR600 cylinder head, ported, gas-flowed and skimmed. Dyno test results
CBR600 36mm carbs (Hornet 34mm), matched inlet tracts, BSD-modded jetting, K&N filter, stock cams, valves, pistons, rods and crank, full Arrow stainless/carbon exhaust system.
Transmission : Stock Hornet box, 14 tooth engine sprocket
(15 stock), stock final drive, 520 DID chain.
Chassis : Metmachex swing-arm, stock wheelbase,Ölins shock (adjustable ride height, preload, compression, rebound), stockHornet forks with gold nitrided stanchions, resprung and revalved to BSD spec, Sprint steering damper, Renthal CR250 motocross bars, stock Hornet yokes, BSD adjustable aluminium footrest risers, LSL titanium FireBlade rearsets.
Wheels and Tyres : Dymag three-spoke 3.50 x 17 front with Dunlop D207RR 120/70, 5.50 x 17 rear with 180/55.
Brakes : Front: AP Racing adjustable span and ratio lever and master cylinder, Goodridge lines, Carbone Lorraine SBK-3 pads,stock 2 pot opposed calipers, 310mm PFM superbike upgrade discs. Rear: stock apart from Goodridge lines.
Other bits : Spa digital clocks (speedo, tacho, oil, air temp, shift light) with memory facility, BSD perspex fly screen, stockheadlamp, standard seat unit with grabrail removed and mesh louvres, BSD crash bungs, carbon alternator cover, BSD belly pan.

All parts are available as individual items.

What makes the trickiest Hornet
in the world.

Engine
We did the motor first to get more power low down and usable, not top end, and lose the terrible 550rpm flatspot Hornets are famous for. We fitted the head from a 1997 CBR600 – it goes straight on, but it's better because it runs 36 instead of 34mm carbs, and hasn't got the Hornet's air bleed into the exhaust port to clean up emissions – part of the reason for the flatspot. Hornet engine

Before we fitted the head we ported it, and skimmed it to raise compression. But we didn't go over the top – we weren't looking for ultimate peak performance, but for overall driveability. Some tuners offer high states of tune but they're about peak power and getting the highest dyno figure they can. Our tune lets the bike drive from 2000rpm in top gear, and it just goes off the throttle, clean with no glitches.
We've gone from 82 to 92bhp, with a healthier torque curve and a much better mid-range. We could go further – 100bhp if we wanted, it's easily achievable – but the bike would be less rideable, which we don't want.
We've ended up with 92bhp – on par with a 1997 CBR600 but peaking at lower revs.

There was a temptation to big bore it, early Blade pistons go in nicely so we've heard, but we didn't want the nasty side effects you get with a bigger engine, like overheating.
We didn't want to have to fit oil coolers and bigger rads and stuff. We also liked fitting a Blade engine but decided against it because although it fits, it doesn't look nice and there's nowhere to put the airbox and carbs. So you end up with sponge filters, which throws up some nasty carburation at the bottom end and isn't good when it rains. We do a mod at the rear of the carbs to accept the airbox, and we alter the jetting to get the fuelling spot on.
Hornet Spa clocks

Suspension
Öhlins speaks for itself. Fully adjustable, the proper stuff. We sell the shock set-up to order – we help you choose the right spring for your weight, and we'll supply it fitted. Mind you, there's nothing especially wrong with the stock shock, but if you push it hard on a track it'll chew up tyres.
The gold nitrided forks look good but it's what's inside that's more important.
We let our results do the talking – our fork conversions came first and second in the Hornet Cup.
What about road-riders? Hornet Dymags and vented disc

The stock suspension is a compromise set-up for the learner road riders and caters for manhole covers and potholes – not racetracks. But for harder road riding, the mods we developed for racing come in useful.
Basically, we re-manufacture the damper assembly using our own seals so the damper actually works. It involves removing a damping valve from the bottom of the leg, machining a circlip groove into the bottom of the leg to re-fit the valve, making new sealing rings, then altering the size of the holes in the damper rod (the size dictates the speed of damping).
We developed the set-up over the first season of Hornet racing – a lot of trial and error went into optimising the system. And, once we'd done all that, we still had to decide what rate spring to use, the amount of oil, and its viscosity. For example, light riders want a 7.5 weight oil, heavier lads need 10W. Then we tailor the airgap to how much and how quickly you want the fork to compress.
And there's another trick – in the base of the fork leg, the bump stop covers some of the holes in the damper rod – we machine it back so the holes work. You gain 5-10mm fork travel too.”
So how does the road set-up differ?
We simply make the damper holes bigger – it makes the forks more forgiving and feel softer.
We spent hours at night playing with them to get them to work. It's so pleasing when you get a standard fork and you compress it and let go and it goes boink. Then you do the same with one of ours and it goes shhhhhh.
Hornet exhaust and vented seat

Rear Sets
Hornets have a hideous rearset plate with the pillion footrests attached to it. We looked for rearsets, but no-one makes any for the Hornets. So we made an adjustable riser plate, which accepts a common rearset – FireBlades are about as common as they come and everyone makes a set of rearsets for them, so they were the ones to use.
Now you can use what you want – Harris, LSL, you're not tied to a particular shape.

Swinging Arm
Matmachex made a one-off for our first Hornet, so we went back when we had more to make. We altered the design a little – the first one was longer to make the bike easier to wheelie.