Suzuki GSX-R 600

The handling improvements are the result of many things. The tyres, for instance, are specially designed for the 600 by Pirelli. The GSX-R wears new Dragon Corsa Evo S tyres. The S indicates they are nearly 1kg lighter than standard models, which greatly reduces gyroscopic effect and unsprung mass, helping the bike to flick over and making the suspension more responsive.

To complement the tyres, the GSX-R gets new wheels in the style of the 750. The diamond tri-spoke design saves 350g from the front wheel and l00g at the rear. The biggest weight saving on the rear comes from the cush drive assembly and sprocket (which is smaller) and saves another kilogram - further aiding flickability. A lighter chassis does its bit too - down 7kg kilograms. Two of those kilograms are shed from the frame, which is still a twin-spar aluminium affair and looks similar to the old one, although its rigidity-to-weight ratio is claimed to be ten per cent better. The frame is also shorter in length and height, and the main beams are one centimetre shorter height-wise to save weight. The other 5kg is made up of smaller weight savings on other components.

Although the weight savings are certainly noticeable, the bike still feels substantial. With bum on seat, it's difficult to tell apart from the 750 because it feels the same size and handles equally well. With a little bit of leg and some bar input, the thing drops on its ear and takes a line requiring considerable neck-twisting to see where it's headed. It feels planted too - in the same sense as a building with deep, deep foundations. The only time it moved was in the later sessions when I was experimenting with how far the GSX-R would lean. And the answer is a long way. It feels like shoulders need moving before the pegs touch down. Even once grinding, there's more to come before the rear moves onto the lip of the tyre. Once the bike is into corners it's incrediblly easy to get on the gas. The GSX-R600 gets fuel injection this year and it's every bit as seamless as the 750's. It was only after two sessions, when I heard someone else talking about it, that I remembered it was injected.

That's not to say it's not impressive in its delivery - it is, it's just so smooth. The engine pulls like they've hidden an extra lOOcc in there and kept quiet. Then it really gets going at 8000rpm, where it'll pull past the redline at 14,500rpm and to the rev-limiter 500rpm later. Something which is very useful on the track -where this bike is designed to be. Unfortunately, we didn't get chance to ride the bike on the road. Not that it mattered. It would only be tempting to start comparing it to the other 600s, something that's difficult to do unless you ride them back-to-back. As it is, on the track, this bike has moved 600s on so much that you have to get used to riding them again. Which can only be good. It feels like it has more midrange and more power than last year's bike but these are difficult things to judge on a track. Only time, a group test and a dyno will show if Suzuki's GSX-R600 will make as big a splash as the 750 has.

For now though I'm off to the betting shop. I've got a pretty good tip and it's arriving this month.

Year after year, the most important thing manufacturers can do to their bikes is make them smaller, lighter and faster. Oh, and they need to have improved handling too. And nowhere is this more important than in the 600cc class. To achieve this, new materials and new technologies have to be thrown at the bike -exactly what Suzuki have done to the GSX-R600.

Many of the features on the bike aren't new -they've been tried and tested on the GSX-R750 which proved itself this year. But knowing stuff works is no bad thing. The previous GSX-R600 was criticised for its racey nature. In other words, it worked best when you wrung its neck. So the 2001 GSX-R gets an all-new motor.

Top of the design brief was to improve the combustion efficiency and reduce mechanical friction. Which means they wanted it to deliver more power - and they claim to have succeeded to the tune of 4.5%. If this is accurate, we should see a genuine 93.4bhp and 47.9ft-lb on the dyno, as we measured 89.4bhp and 44ft-lb on the old bike.
Improving combustion efficiency simply means making better use of what goes into the engine -petrol and air. The idea is to burn the mixture and use it to increase the pressure inside the bore which forces the piston down, turning the crankshaft. Instead, some heat from the burn escapes into the metal of the engine meaning wasted energy. To help the 600's efficiency, Suzuki looked at the SRAD air intakes. These have been moved slightly closer to the nose, where the highest pressures are found. This causes higher positive air-pressure inside the airbox the faster the bike travels.

From there the air is fed into a larger, 11.3-litre airbox (up 1.3 Litres) which now uses a flat air filter, rather than the old cylinder-type. Finally, the filtered air heads into the engine through bell-mouths, something the old bike didn't have. These provide a smoother flow by channelling the air and are shaped to work with pulses caused by the valves opening and shutting, so when the inlet valve opens a positive pulse is waiting to start the charging process. Next, and most notable in the line of improvements is fuel injection. The GSX-R600 now uses four, 41 mm in, 38mm out throttle bodies. The old 600 had smaller 36mm in, 36.5mm out carbs. Each of the four bodies incorporates the SDTV (Suzuki Dual Throttle Valve) system. As the name suggests, there are two valves in each body.

The primary valve, the one closest to the engine's intake, is controlled by an oval-shaped pulley connected to the throttle. The oval shape means the ratio between twist-grip movement and throttle valve movement changes. At small throttle openings you get small movements, but from mid-to-full openings it behaves like a quick-action racing throttle. The secondary throttle body valve is controlled electronically according to engine rpm and gear position. Its job is to maintain optimum air-flow speed (intake velocity) when the rider opens the primary valve. It may sound odd to maintain intake velocity by putting more stuff in the way, but it isn't.

Take a sand-type egg timer and imagine it's the throttle body. Think of the sand as air and the narrow bit in the middle as the secondary valve. When you turn the timer over, the air at the top moves so slowly it looks like it's not moving at all. The air running through the middle is moving quickly - and the primary valve is just below it.
Maintaining maximum velocity over the primary valve is important as it helps to mix the petrol sprayed from the injector evenly. The better the mix, the cleaner the burn will be - which comes back to Suzuki's quest for combustion efficiency.

But the SDTV is not the only change from the norm. Usually, injectors are mounted to aim at the intake valves to improve throttle response at low rpm, but because this arrangement sprays fuel in the same direction as the air-flow, fuel tends to run down the throttle body walls at high rpm.

On the GSX-R, the injectors are mounted at 60° to the air-flow, but because the secondary valve creates a high speed, turbulent airflow, good atomisation is still achieved at low rpm. The high speed mixing problem is solved because the 60° angle means the injector is partly aimed at the primary valve. The idea is that when the valve is halfway to fully open half the spray hits it. This makes the spray even finer and mixes it evenly through the throttle body.

From there the mixture enters the 600's new cylinder head through straighter inlet ports -something that was helped by the narrower valve angle. The straighter ports improve the engine's Secondary throttle valve maintains intake velocity when the primary valve is opened volumetric efficiency, which is its ability to fill each cylinder in the time the valves are open. Narrowing the angle of the valves, so they sit more upright, reduced the combustion camber's size and raised the compression ratio from 12:1 to 12.2:1 while making the charge easier to ignite. The size and weight of the cylinder head is also down.

The valves themselves are lighter as the stems have been reduced from 4.5mm to 4mm, saving 48g, reducing inertia and creating less resistance to gas flow. The inlet valve diameter has been increased from 26.5mm to 27.2mm to help volumetric efficiency. Closing the valves are single spring made from alloy spring steel, rather than the inner and outer spring steel jobbies. The camshafts are also made from new, lighter material to reduce inertia. The second part of Suzuki's mission - reduce mechanical friction - is most evident in the crankshaft. Mechanical friction is the loss of power caused by moving parts in contact with each other - and one of the most significant places to find it in an engine is the crank journals.

It follows that the larger the diameter of those journals the greater the friction. So to reduce the losses, the GSX-R's journals have been reduced from 34mm to 32mm. The crank pins have been reduced in diameter too, from 32mm to 31 mm. Another main source of mechanical friction is the pistons reciprocating in the bores. To reduce these as much as possible the bores are lined with SCEM (Suzuki Composite Electrochemical Material). This has better heat transfer characteristics than cast-iron liners, which means tighter piston-to-cylinder tolerances can be run. This in turn means low-tension rings can be used (reducing friction) without compromising sealing.