2004 Suzuki GSX-R600

When a 2% Improvement is the Difference
Between 4th and 1st.

The US economic recovery is about to get a big boost as hundreds of racers purchase new bodywork, pipes, brake lines, clip-ons, rearsets, manual cam chain tensioners, valving for front forks and purchasing valve jobs and head skimming because Suzuki Cup racers will be able to qualify on their 2003s, but the winner at Road Atlanta in October will be riding a 2004.

The not-so-elusive GSX-R in its native habitat. It’s the 2003s that are now endangered.

This time the step in performance and technology is not as great as jump from the 1997-2000 generation GSX-R 600 to the 2001-2003 GSX-R. At that time the 600 lost 24 pounds and gained about 10 bhp through an all new engine, fuel injection and a new chassis. Although some of the changes are substantial (chassis) many of the updates are small (motor) so the raw improvements only boost power by 4% and drop weight by 1.2%. Although the paper improvements are minor, when coupled with the much improved brakes, stout front forks and new over-rev capability the 2004 will be able to edge out the 2003 enough such that at least the first five rows of the GSX-R 600 Suzuki cup race at the Grand National Finals will consist of 2004s.

Smoke off a knee slider on stock tires in forty degree temperatures indicate that this chassis has feedback
or an idiot riding it.

Because the 2004 is not yet available (Suzuki officials say February, my local dealer says April) hundreds of middleweight racers are in the unviable position of having to start the season on their 2001-2003 GSX-R while buying the 2004 and performing all development work during the actual race season. The good news for novices and track day enthusiasts is the vast amount of 2001-2003 GSX-R’s which are just about to become available by the up-graders who have to have the latest thing. This is indeed good news because a race prepped 2003 is still a formidable weapon but in equal hands the 2004 has enough small advantages to turn the faster lap times. Such is progress.

We tested the bikes on a very cold day (40 degrees) at the Misano circuit in Italy. We tested the bike with the stock European spec Bridgestone tires which, too be fair, worked pretty well in the adverse conditions but were simply not able to give enough grip/confidence to really throw the bike around or test the limits of the front forks under trail braking. That means, dear reader, any real review of the stock suspension will have to wait until a warmer date.

Today Misano, In October, Road Atlanta

Racers, of course, have already budgeted to toss the stock shock and fork internals so the performance of the stock suspension takes a distant second to the performance of the new engine. I think we can be reasonably certain that the new internally braced frame and externally braced swingarm are suitably rigid to handle the traction offered by modern slicks and DOTs, and the forks, when fitted with track spec springs and valving, will be at the front, and probably the lead, of superstock 600s.

The new GSX-R is physically narrower and feels slightly smaller but the overall feel and character is still GSX-R. It still feels a bit bigger than an R6 but it is easier to reposition arms and legs around the more diminutive tank. Suzuki made the whole bike a little narrower but took a major shortcut with the physical size of the gas tank by just dropping the capacity by a full liter. The minor changes to the handlebar and footpegs are not blatantly obvious when straddling the bike.

Although small but not cramped…for a race bike. 

In stock trim the 2004 has three immediate and noticeable improvements over the 2003.

  1. The bike now revs to 15,500 rpm (a la R6) with peak power around 13,500. The extra
    revs allow the rider to simply wind the bike out on short chutes without having to do the
    quick upshift/downshift dance.
  2. The brakes, which were always strong, are now incredible. Although the radial mounted
    calipers look trick the big improvement is more due to the radial master cylinder. Radial
    master cylinders deliver more fluid with less effort than conventional master cylinders,
    which increases sensitivity and braking power.
  3. The bike is smaller which makes it easier to toss around between the knees and to flick
    side to side.

The engine is very revy but I would be hard pressed to say that I could actually tell that it had 4% more power than the old model. The fuel injection works perfectly and the bike picks up speed very quickly all the way to its 15,500 redline. As you might expect with a race platform bike, torque has been sacrificed to the god of horsepower so if you try to exit a turn below 10,000 you are in for a bit of a wait before the engine gets back on the boil. The FI delivers clean power so if you have time to wait there is no problem in letting the engine lug from 6,000 rpm or so but you better be just pulling on to a freeway, not trying to beat your season long rival from turn 6 to turn 7 at Road Atlanta.

The closer ratio transmission is crisp and secure. All of the ratios above second gear have been tightened up a little to make it that much easier to keep the engine in the happy part of the powerband. The clutch engages smoothly and is easy to modulate to avoid back torque induced wheel hop.

The new frame geometry is slightly more aggressive than the ’03 but since all racers mess with the ride heights both front and rear it won’t make much of a difference as few will leave well enough alone. The new frame is physically smaller but should be more robust than the fragile welded spars of the 2003. I certainly could not feel any downside to them and they both look terrific. Even with stock springs and stock tires (actually they were the stock tires for Europe since Europe gets Bridgestones while the US models are fitted with Dunlops) the GSX-R handled with its historic precision, accuracy and confidence.

Perhaps the Cyclops looks is an acquired taste.

Racing against an R6 the ’04 GSX-R rider will have parity on engines and will be armed with superior brakes and equipped with the better forks. To compete with this bike Kawasaki will have to have increased the engine output of their bike substantially one year after its introduction which is unlikely. The Honda 600 needs to lose a prodigious amount of weight which is equally unlikely one year after introduction. If you are serious about middleweight racing and/or plan on contesting the Suzuki Cup you might as well suck it up and place your deposit now.

Ten years ago this would have been considered a trick fork on a superbike, today it's yours. 
Let the aftermarket be forewarned.

And they will all be available in the US, sometime.

Technical Details and Other Insights

The 2001-2003 GSX-R 600 was based on the 750 platform which made for an unnecessarily wide chassis and engine. The 2004 has been slimmed down, lightened up and had a few small tweaks to boost power and potentially increase reliability.

The best place to pick up intake air is at the nose of the fairing. Since Suzuki likes the way headlights look right there the GSX-R has to have the air intakes on either side. The 2004 has been slightly optimized in this regard by stacking the headlights and moving the intakes 25mm closer together. This, in theory, increases power at high speeds. Due to smaller frames spars and a smaller and narrower fuel tank (30mm), the front fairing can now reduce the width of the entire bike by 43mm.

Air intakes now 25mm closer to center.

The engine castings will look very familiar to GSX-R racers. Although the head width remains constant the internal ports, valve guides, valve train and included valve angle have changed. The cylinders have been shortened by 3mm (by shortening the rods by 3mm not usually a good thing) which saves 200 grams. The bottom of the cases now have a smaller (30mm versus 32 mm) crank journals and have 35mm ventilation holes beneath the crank bearings to cross ventilate the pistons to reduce windage and pumping losses. These cross venting holes apparently increase top RPM torque by 2%.

Suzuki has reduced the included valve angle by 4 degrees which allows for a slightly more compact combustion chamber boosting the compression ratio from 12.2 to 12.5:1. Since the combustion chamber is smaller Suzuki employed 18gram lighter flat- topped pistons to improve the burn in the cylinder. Typically manufacturers run domed pistons to increase compression but all the topography on the top of a piston interferes with flame propagation so, in this case, flat is better. The pistons have chrome nitrided upper compression and oil control rings compared with the typical normal chrome plated rings. The intake port has been straightened further but making it 5 degree steeper and the exhaust ports have been enlarged by 2mm.

The fun stuff is mounted in the head. A first for 600s (but old hat in four-stroke dirt bikes) are the titanium valves. Titanium is about 2/3 the weight of steel while having superior strength and thermal properties which reduces the weight of the intake valves by 5.6 grams each and the exhausts by 4.4 grams. Being lighter means less inertia that the valve springs need to fight to keep the lifters following the cam profiles at 15,500 rpm. The 10% lighter valve springs reduce friction and the wasted energy that four-stroke engine spend opening and closing valves. Taking this theory a little further Suzuki also reduced the diameters (and weight) of the lifters. But the best news is yet to come, steel valves with 4mm valve stems (ala 2001-2003 GSX-Rs and many R6s) break. This means regular and costly complete valve train replacement on the older bikes. The ’04’s valves have 4.5mm valve stems, which should greatly decrease the likelihood of a similar reliability problem occurring on the ’04. Of course, the spring retainers might break like the ones in the 2000 GSX-R 600 but we’ll cross that bridge when we come to it.

The lighter valves are all about increasing the redline, weight and reliability because the cams, although lighter (In=-45g Ex=-35g, by having an even bigger hole drilled through the middle of the cams) they have the same lift as the old cams and the intake actually has a few degrees (7 to be precise) less duration than the 2003.

The ’04 routes oil pressure to the cam chain tensioner through an internal passage, which allowed for the saving of 80 grams of weight by eliminating the oil hose. Racers should immediately save a little more weight by ditching the failure prone automatic cam chain tensioner for a manual tensioner from the manufacturer of your choice (we use APE but you can use whatever you want). Holding the revised head to the revised cases are revised and lighter waisted head bolts.

In addition to having closer ratios the transmission gets a revised design of the shift fork buttons to improve shifting feel. The clutch has been beefed up for the added power by increasing the spring load by 4% but the springs have a 25% lower spring rate to reduce lever effort.

The extra heat from the higher redline is dispersed by two revisions to the cooling system. The oil/water heat exchanger has gained 2 layers from 6 to 8 which increases its ability to dump 3.8kw of energy instead of the 3.35kw of the 2003. Dumping more heat from the oil into the cooling system is no good unless you can disperse the additional heat out of the radiator. The radiator’s cooling capacity has been increased 8% by being made 10mm taller but the weight has been reduced by 125 grams by making the radiator thinner (-2mm) and narrower (-40mm). Street riders will benefit from the fan with the new style integrated blade shroud that is slightly more efficient than the old style.

The ’04 fuel injection has several refinements including simpler (two castings instead of four) and lighter (370 grams) throttle bodies that remain 38mm in the primary throttle butterfly but are 5mm larger (46mm) where the computer controlled secondary butterfly is located. The new throttle bodies have lost the manually operated fast idle in place of a computer controlled fast idle based on water temperature. Like the 1000 the 600 is fitted with multi-hole-type injectors instead of the older pintle-type injector. The new injectors improve atomization of the fuel increasing torque by 1% across the powerband. The airbox is 10mm shorter and 20mm narrower to allow for the smaller gas tank.

Irrelevant to most US racers the 2004 European model gets a catalytic converter in the muffler. To eliminate power loss from the element in the exhaust flow the muffler capacity has been increased from 4.9 liter to 6.9 liters. To keep weight gain to a minimum the muffler now features titanium internals but still has the aluminum external skin. Emissions are further reduced by increasing the size of the internal head passages for the Pulsed Air Injection System that feeds fresh air into the exhaust pipe to continue the combustion process in the exhaust pipe and reduce un-burnt hydrocarbons.

The ’04 gets a more powerful ECU featuring a 32 bit CPU (up from 16-bit) with a full 256 K of memory. The ECU is now 80 grams lighter and physically smaller. To increase the precision of the fuel injection (perhaps required by the higher RPM) the 2004 is fitted with a 22 trigger point signal generator instead of the 8 points of the 2003 model.

There are a few other small electrical refinements like the LED taillight and stacked headlights. The instrument panel basically remains unchanged but gains a basically useless, but user configurable, shift light.

The chassis has been extensively redesigned for a variety of official reason (stiffer, smaller) and a few unofficial reasons (simpler to make, reduces frame damage from sub-frame tabs snapping off in light crashes). The 2003 frame featured some time consuming fabrication due to the amount of welded required to assemble the spars from multiple sheets of aluminum. The ’04 uses time saving extrusions, which also allow for smaller spars (15mm narrower from outside edge to outside edge) without sacrificing rigidity due to the internal bracing. The subframe now bolts to a much larger (and hopefully stronger) piece on the frame than the 2003.

The rake has been decreased from 24 degrees to 23.25 and the trail has been decreased 3mm. Fear not, the GSX-R comes stock with a non-adjustable steering damper.

Carefully modulating 23.25 degrees of rake.

The gas tank is a full 30mm narrower at the knees and the footpegs have been moved together by 10mm. Unfortunately the narrower tank also means a smaller tank and fuel capacity has dropped from 18 liters to 17 liters.

When the cold tires tuck, the peg feeler hits first, ask us how we know!

In the back is a braced swing arm that is dimensionally identical to the ’03 but is 5mm narrower at the pivot and is heavily braced. The shock linkage remains unchanged but the ’04 shock is 7mm longer so you may need a longer mount (or shim the top shock mounting point by 7mm) for your ’03 shock if you want to save it and bolt it onto your 2004. Suzuki doesn’t say but the swingarm has to be heavier with the brace but they did eliminate the rear brake caliper torque arm to reduce the weight gain of this subassembly by 170 grams. The stock shock (which should not be automatically replaced by track day riders because it is a good shock for a stock fitment) has some minor improvements including a slightly stiffer spring and a bigger damping rod (+2mm to 16mm).

Bolted to the front of the black frame is a tasty Showa inverted fork, which features sliders fitted to allow for radial mounted brake calipers. The excellent fork is a bit over shadowed by the brakes. The Tokico radial calipers are flex resistant and look great but the big winner is the radial master cylinder. Radial master cylinder has better mechanical leverage. Better mechanical leverage allows for a bigger piston (in this case 19.05mm up from 15.87mm which look like funny measurements until you realize that brake master cylinders, like wheels, are still typically measured in Imperial), which means much higher pad pressure with the same lever effort. This allows for sensitive braking as well as out and out braking power. The Suzuki has a pretty damn good brake pad fitted as stock. The improved calipers and master cylinder allowed Suzuki to use smaller (and 40 grams lighter and remember this is unsprung and spinning weight) rotors but have been made thicker (5.5mm compared to 5.0) to handle the increased heat.

All of these revisions add up to what promises to be the dominant middleweight racing platform of the year.

Also available in Yellow.


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