Suzuki GSX-R 750
Don’t ask why, ask why not?
For six years Suzuki has completely and utterly dominated what used to be the most hotly contested sportbike class. One by one the other Japanese companies brought great shame to themselves by capitulating the class to Suzuki until they were the only one left. As the world racing class structures moved to 1000cc and the AMA followed suit some folks have been left wondering why Suzuki still makes the 750. The answer should be pretty obvious. They sell a lot of them to street riders, most of their racer sales were not to AMA racers in the first place and they make a ton of money off of the bike.
Any more questions about why Suzuki still shows up with the 750?
This bike is going to be sold to basically three groups. 750cc class racers (of which, we all know, that despite the AMA having dropped the 750 class there are still plenty of classes for 750s including Suzuki’s own lucrative Suzuki Cup Series and the less lucrative but more romantic World Suzuki Cup series, the final of which is being held in conjunction with the WERA Grand National Finals this year at Road Atlanta.) will have to buy ’04 GSX-R 750s if they are interested in running at the front. Like the 600, the new bike has enough small advantages to make it, in equally talented hands, the race winning machine over the ’03. The next group is track day enthusiasts. The 750 will make an excellent track day bike because most track day riders (and don’t be offended here) can rarely use the full power of a 600 let alone a 1000 and the 750 makes a good compromise between the 600’s superior handling and liter class “oh shit this fucking thing is fast”.
When you really narrow it down it’s largely about crank weight. Cranks, spinning at 12,000 to 15,500 rpm create a very powerful gyroscope across the centerline of the bike. Unlike the gyro action of the wheels (which are speed related) the crank gyro is with you any time the revs are up. This bike has a much lighter crank than any 1,000 which allows the bike to steer with less effort at both high speeds and high RPMs as well as low speeds and high RPMs.
The Ryuyo track is Suzuki’s proving ground which would ordinarily be used to test bikes but also to perform such banal tasks as interior noise testing on Grand Vitaras. That means, unlike a racetrack, there is absolutely no run off on the outsides of the turns. It has only two slow turns and the rest are fast sweepers. Some are very fast sweepers. The back straight is so long that, even entering it in second gear, the bike quickly reaches the maximum top indicated speed of 299 kph about 2/5s of the way down the straight. That’s an indicated 180mph but I think it is safe to assume that the speedo is about 10% optimistic.
With a good drive onto the front straight it was possible to hit 6th gear as well. Coming off the front straight is a fast left right combination and its lined with walls. At the apex of the right the speedo was indicating 286kph at 13,750 rpm in 6th but the bike would still steer through the right left without having to fight the bike or even pull too hard on the bars. That’s a light crank. Less important for the performance enthusiast but good news for sufferers of carpal tunnel everywhere is the very low level of vibration in the handlebars. After riding liter bikes for the past few weekends the smoothness of the 750 motor stood out.
After years of having Suzuki having a reputation for building absolutely bulletproof transmission and clutches there was a spate of transmission failures on the GSX-R series over the last few years. Although the most common problem was a shift bolt backing out in the motor there were also problems with overly lightened shift shafts and problems with gears, shift forks and shift drums wearing out much faster than in previous years. Although one day on a track is not sufficient to see if the wear problems have been remedied in this new generation of Suzuki I can tell you that the shifting in a new bike is just about perfect. A thoughtless snick from the foot either up or down, clutch or no clutch, was all that was required to securely and confidently stick the requested gear. No drama. No second thoughts. No hesitation. It’s the way transmission should be. Kawasaki engineers should buy one of these and reverse engineer it. Yamaha engineers can just take a look at the notes that the Kawasaki guys draw up.
The clutch is a straightforward cable operated traditional clutch that did all those clutch things you want a clutch to do without any shutter, chatter or fuss. This is true both for 12,000 rpm race starts as well as feathering the engagement on corner entrances.
The brakes are straight off the 600. Trey Batey had mentioned that one of the tricky elements to racing in the World Suzuki Cup race in France last year was that the stock brakes (required by the rules) were not up to snuff which made it really difficult to accurate judge how late one could leave the braking. This bike’s brakes are much more powerful than last year’s. Primarily due to the stiffer calipers (centrally bolt bridged, and radial mounted Tokicos) but fortified with the radial master cylinder (who benefits I have explained in two other articles (GSX-R 600 last month, R-1 this month) so if you haven’t internalized why the radial master cylinder is better go read those other articles. Suzuki still seems to be shying away from a really aggressive brake pad but the stock pads in this bike are much better than what were fitted as standard in previous GSX-Rs. Racers will still want to ditch the rubber brake lines, put in some better fluid (these brakes would go soft sitting in the pits) and fit some sassy race spec brake pads. However, if they have to run the stock brakes in the World Suzuki Cup race, the braking battles into 10a at Road A should be plenty entertaining. The brakes also have slightly smaller rotors that are also a bit lighter. The lighter rotating mass on the front wheel has to be helping the 750 with its nimble steering ways.
The new series of GSX-R have narrower frames and gas tanks making the bike much less intrusive into the rider’s space. The 750 is narrow enough to comfortably get up on the pegs and flick the bike underneath you from left to right without having the mass of the bike tangle up with your knees or elbows. The new narrow form factors makes it easier to get comfortable in a race tuck or knee down.
The shock and forks are the same units are fitted to the 600 including spring rates and valving but the 750 comes standard with slightly stiffer settings. When the factories first started fitting adjustable suspension to sportbikes they solved one problem and created a new one. Many people, journalist included, don’t know how to set-up suspension on a track bike and, even if you do, there is often not sufficient time to do it at a press launch. Much to the dismay of the factories, journalists would request improper adjustment changes and then proclaim the bike an evil handling piece of junk. Given that past, the standard practice at press launches is to enthusiastically offer to make suspension changes in the rider’s meeting and then to rigorously discourage anyone from making said changes on an individual basis. The many superfluous Japanese technicians at the track (got to keep that unemployment rate down at 3.8% somehow) standing around my bike in the morning balked at adding any rebound to the forks and all thought it was pretty funny when I used the ignition key to add the extra half turn of rebound myself.
Serious racers will want to have the forks reworked and replace the shock but the stock suspension is much better than stock suspension has been in the past and will be sufficient for many a track day enthusiast and/or street rider. With its stock (but un-adjustable steering damper) the bike was dead solid across bumpy pavement with some grooves and camber at an indicated 299mph, even with brisk oceanic crosswinds. The stock Bridgestone tires (although US market gets Dunlop 218) offered a pleasantly surprising level of grip despite the proving ground featuring two different types of pavement, lots of lateral bumps and, occasionally, being soaked down with brisk oceanic downpours. The unyielding walls lining the track discouraged finding the outright limits on this particular tire and suspension combination but the limits were well above a track day pace and pretty far into the ranks of novice class racing…with the OE tires.
The engine is a bigger version of the new 600. Same bore and stroke as last’s year’s 750 but with titanium valves, the new throttle bodies/injectors and the cross ventilated crank cases. Since the 750 carries quite a bit taller primary gearing (43 rear, 17 front) than the 600 (45/16) the engine performance is deceptive. The first impression is that the 750 is not anymore zippy than the 600 because the revs of the motor don’t really pick up significantly faster than the 600 motor. However, when your brain gets around the fact that each additional 100 RPM is a lot more MPH you can start to appreciate how fast and smooth this engine really is. With the tall gearing (which really wasn’t tall enough for this track, uh, “proving ground”) the engine never feels close to overwhelming the ultra stiff chassis. The engine doesn’t have the torque of a 1000 but it will plain flatten a 600. Once in the power band (pretty much anything above 9,000) the engine pulls cleanly, resolutely and reliably to redline. For big tracks (Road A, Daytona) it could use some longer legs. For the street it would probably be more fun to drop a 16 on the front to make sure you can pull 2nd gear powerlifts. Forgive the shameless namedropping but since Suzuki trotted out the everyman’s GP champion Kevin Schwantz I am going to go ahead and use him. Kevin and I (we’re on a first name basis, I think) were chatting in the break room. Knowing that I had just ridden many of the liter bikes he asked me if the 750 would run with any of the other heavyweights. Before the other Nipponese companies got serious about matching the GSX-R 1000s power output the GSX-R 750 actually had more power than many of the other 1000s. I told him that was no longer the case. In a drag race the R1 or ZX10 would smoke this 750. Well, the ZX10 would win as long as it only had to use the first three gears. Humbly (being humble is one of my strong suits) I offered that for me, I would probably be just as fast around a track on the 750 as the liter bikes because, for my high corner speed riding style, it was more important to have light weight and nimble handling rather than lots of power. I even went so far as to propose that there are relatively few riders that can effectively use the additional power that the 1000s offer, especially given that they all run on virtually the same sized tires when almost all riders will benefit from the reduced weight and better handling of the 750.
Imagine my amazement when Kevin agreed with me.
Search for “600” replace with “750”
The chassis geometry, suspension, brakes and ergonomics are all the same as the 600. The 750 frame has thicker casting at the headstock and swingarm pivot. The 750 only weighs five pounds more than the 600 and virtually all of that weight is in the motor. The 750 motor has a heavier crank, rods, pistons and a taller block than the 600. The 750 motor will bolt into a 600 frame but it would be much cheaper to buy a 750 and replace the tail section bodywork with one that said 600. Pipe, fuel injection and ECU are all different for the 750.
I will, henceforth, try to avoid further discussion or comparisons to its smaller sibling but will henceforth compare it to its predecessor 750.
The ’04 has 4% lighter reciprocating mass in the motor, has 5% more power and 2% more torque. It has a claimed 155.4PS with the new improved SRAD in full effect and weighs 6.6 pounds less than the ’03. It revs 500 rpm higher before running into the cushiony soft revlimiter. It has much better brakes, a smaller form and has mildly improved chassis.
The ’04 sucks air through snouts that provide slightly more air at top speed than the old induction system. It also required the stacking of the headlights which I think are more homely than the old ones but some think are just bitchin’ so I leave it to you to decide. The intake nostrils are 25mm closer together and are aligned more vertically than horizontally as the ’03. This changed allowed Suzuki to narrow the frontal area by 43mm which makes aerodynamic guys get all misty. To help the rider tuck in more behind the narrow fairing the tank is shrunk (literally since it lost a liter of capacity) and it 30mm narrower at the knees and 15mm shorter front to back.
The intake runners dump into a smaller and reshaped airbox that is 20mm narrower (to fit under the smaller tank) and 10mm shorter (see “to fit under the smaller tank”). Suzuki had to squish the throttle bodies tighter as well so the pitch (ie, spacing between the centers of the throttle bodies) is 5mm closer between the outermost bodies while the center two bodies remain at 80mm spacing. The throttle bodies have been changed to the dual dual throttle body design with the resin fuel rail but there internal dimensions remain unchanged with a primary valve diameter of 42mm and a velocity stack inlet size of 50mm. The dual butterfly throttle bodies are fitted with the injectors with the little holes instead of the pintle type whose action is controlled by a new ECU that now has 256 kilobytes of RAM up from 96 on the ’03. This change improves atomization and boosts torque by 1%. The throttle bodies are fitted with a (IMHO unnecessarily complex) water temperature controlled fast idle circuit. The bodies as a whole are 370 grams lighter than those fitted to the ’03.
The air/fuel is then sucked through a slightly larger (2%) intake port, around identically sized but now titanium intake valves that are set at the same angles as before (ie, the head ain’t all that different) which are opened with a lighter (45 grams) cam that is only slightly (+.1mm lift, +6 degrees duration) bumpier. The Ti valves are closed with springs with a 25% lighter spring rate which reduces lost energy due to opening and closing valves.
The 187.25 cc is then squeezed into a 16.5cc combustion chamber (.5cc smaller than before) giving a compression ratio of 12.3:1 (up from 12:1). It should be noted that the smaller combustion chamber is not due to narrowing the valve angle but by shrinking the chamber with the shape of the piston tops and the face of the valves.
The 15gram lighter pistons take the bang. These pistons are that same bore but are 1.5mm shorter and have a narrower skirt. The pistons are fitted with low friction chrome-nitride compression and oil control rings. The new finish on the rings reduces power losses due to ring/cylinder wall friction. The ’04 gets a critical dimensionally identical rod to the ’03 but it is “changed in detail” to take the extra power. The crank is dimensionally unchanged from the ’03. The 750 cases get the 35mm holes under the main bearing journals to cross ventilate the cylinders and reduce pumping losses.
The exhaust is then blown out past the new titanium exhaust valves which are held open for just this purpose by a cam that is 35 grams lighter (with a bigger center bore) but with unchanged bumps. Once around the valves the blown gases get to make use of a 32mm (+2mm from’03) exhaust port. The ports feed into a stainless steel 4-2-1 system with a bigger muffler (+10mm OD, +8mm ID and +90mm length, + 2 liters in volume which is about a 40% increase) that sports titanium internals to reduce weight. European bikes get a catalyser in the muffler. Emissions are controlled by a reconfigured but functionally similar Pulsed Air Injection System (PAIR) that allows the vacuum in the exhaust pipe that follows the energy wave in the pipe after the exhaust valve opens to pull fresh air from the air box into the exhaust pipe. The fresh air allows hydrocarbons to continue to burn in the exhaust pipe.
The extra heat caused by this improved sucking, squeezing, banging and blowing is transferred to the atmosphere from the oil using a 33% bigger oil/coolant heat exchanger and coolant/air heat exchanger that has 12% more capacity by being reshaped to be both larger but also with a more pronounced trapezoidal shape. Its wider at the top (412.6 versus 380mm) taller (298 versus 238) and narrower at the bottom (252.9mm versus 380mm). Core thickness is unchanged at 24mm. The cooling fan now has the integrated ring and is more efficient while being 135 grams lighter.
The cam chain tensioner is hydraulically controlled with an internal oil line to drop 80 grams by eliminating the older external line. I don’t have any faith in Suzuki cam chain tensioners so I would replace this with a manual one if the bike is going to see any track service at all. I will happily announce my endorsement of the stock Suzuki cam chain tensioner when I get a notarized letter from any member of the senior management team at Suzuki personally guaranteeing me that I will never see another Suzuki cam chain tensioner strip or crack apart and drop parts into the motor. Send the letter to the Roadracing World offices.
The motor is bolted into a new chassis. The frame is all new and is narrower. The new 43mm front forks are re-positioned to reduce trail by 3mm to 93mm and to reduce rake to 23.25 from 24mm. That is, by the way, some seriously quick steering geometry. The frame uses smaller spars but is now internally braced through the use of extrusions for the main spars. The new frame and tank result in a bike that is 30mm narrower at the knees and 10mm narrower at the footpegs allowing the ’04 a 55.5 degree bank angle which is 1 degree more than the ’03. The detachable subframe bolts to main frame in an improved manner which is intended to reduce main frame damage from blunt force trauma to the subframe. The swingarm is dimensionally the same at the ’03.
The front forks are still 43mm inverted Showas with 120mm of travel but they have different bottom bosses to accept the radial mounted brake calipers. The rear shock has got a bigger rod (16mm instead of 14mm) and is 7mm longer but I believe the linkage ratio is the same. The wheels are fundamentally unchanged at 17x3.50 front and 17x5.5 rear.
The big news on the brake front is the radial mounted Tokico calipers that benefit from the inherent strength of the radial mounting as well as stout anti-flex bridge across the middle of the caliper. The aluminum piston sizes are unchanged with 30/34mm. The calipers are mated with smaller (300mm instead of 320) and lighter (-20 grams) rotors. The calipers are pressurized by a Nissan radial mount master cylinder that is 19.05mm up from 15.87.
The rear brake has been switched from a Tokico to a Nissan and the mounting has lost the torque arm. This set up has lost 170 grams.
Without any competition at all Suzuki has improved the ’04 enough to render the ’03 obsolete as a racing platform and to keep it close to the liter class but they have not made the serious investment required to make the engine narrower (to match the narrower frame) or to produce a head with different included valve angles. The 750 is a great bike but it looks like Suzuki is holding back some tricks in case any other manufacture returns to the 750 class.
The new frame has got the snap off resistant subframe tabs, is painted black and is presumably is easier to make than the old frame.