Gsx-R 200g

GSX-R 200G

ROUNDUP

LESS REPLI, MORE RACER

I LIKE WRITING ABOUT engineering changes that make sense-in this case for the 2006 Suzuki GSX R600 and 750. Sportbikes, like fighter aircraft, are mar keted on the basis of what they can do-performance is king. Sales competition drives bike performance, pushing up power through higher revs and reduced fric tion, forcing chassis revi sions to handle the result. Price is also king, so accu mulating design experience must cut the number of parts, welds and minutes of human labor required to build each unit. This is a subtle game, and Suzuki is an experienced player.

Wheelies impress novices, but once the front wheel is up, you can't steer out of a corner, and more throttle opening just breaks taillight lenses. The steady rise of power and tire grip forces racers to pull their weight as far forward as possible as they accelerate, helping to make the front tire steer and the bike turn. When such ath letic compensation reaches its limits, you move major masses forward-yet the engine is already as far for ward as possible. The 2006 answer is, as in MotoGP, to redesign the engine to con centrate more of its mass for ward by vertically stacking the gearbox shafts. This requires a longer swingarm (a clear trend in MotoGP), which eases suspension com promises to keep the machine from squatting and pushing in corners.

Both GSX-R600 ($8799) and 750 ($9999) gain power from an improved, more open

combustion chamber, a slight increase in compression and a higher rpm limit. Because combustion tends to be slug gish in large-bore, shortstroke engines, the 750's bore is cut from 72 to 70mm, and the included angle between intake and exhaust valve stems drops from 25.0 to 22.5 degrees. The smaller bore and flatter head shorten flame travel and better retain com bustion-speeding turbulence. Bringing the 750's bore clos er to that of the 600 simplifies use of shared tooling and saves weight in the 600. The 750 loses 1¼ inches in height, 2/3 of an inch in width, and is 2','3 inch es smaller front-to back. The 600 loses an inch of height, 2 inches front-to-back, and is also 2/3-inch narrower. The smaller you make the engine, the wider your choice in where to locate it and associ ated parts.

A longer stroke and 600 more peak revs push 750 piston acceleration up 15 percent. More fatigue-resis tant parts handle the increased stress-shot-peened connect ing rods, a chrome-moly steel alloy forged crank and forged-aluminum pistons of beautiful organic shape that eliminates stress-concentrat ing sharp edges and sud den changes of section. Feast your eyes. To save chassis and rider from increased second ary shaking force, a small, two-times-crank-speed bat ancer shaft is fitted.

New cylinder head on both 600 750cc GSXRs fea tures more-aggressive cams I titanium valves. Higher revs further load engine internals, and - contours of piston structure resist failure. Minimalist crankshaft is forged `chrome-moly steel for the same reasons. The Qff dyno awaits~.

The 600's bore and stroke remain as before, at 67.0 x 42.5mm, but peak rpm is up 500 and its combustion chamber has also become more compact via reduction of valve included angle to 22 degrees.

Bigger “breathing holes” in main bearing webs (both engines) cut pumping loss as pistons push crankcase air back and forth almost 500 times a second at peak revs.

Above the pistons, the 750’s intake valves remain the same size but, owing to the 2.0mm smaller bore, had to be moved slightly. Room comes from use of 1.0mm smaller exhaust valves with improved ports. This technique of trading exhaust for intake area comes straight from Formula One car racing. Both engines receive dual fuel injectors per intake-one below the throttle for low/midrange operation and a second above it for higher rpm.

The 750 and 600 are built on a 55-inch-wheelbase, twinbeam aluminum chassis with assembly simplified by a reduced parts count of all cast components-no more extrusions here. With engine mass concentrated forward, these bikes can accelerate harder than before without lifting a wheel. In place of the former long “RFD mailbox” mufflers, the header pipes loop ahead to pull the whole exhaust system forward under the engine, leaving only a short, MotoGP-style outlet just behind the rider’s right heel. A shorter fuel tank moves the rider forward, as well. A shorter suspension unit lowers the seat, as mentioned before. Tighter packaging of machine and rider equals faster maneuvering.

Style is clearly from MotoGP, featuring a short fairing that reveals the housing of the back-torque-limiting clutch.

Tumsignals integrate into the mirrors and seatback, while the short exhaust blends into the fairing. Aero drag is said to be down 5 percent. Even with progress in every category, there is no ultimate. You can bet that plans for next year’s model are already well-advanced.

-Kevin Cameron