Yamaha builds very rapid 600cc fours going all the way back to the '84 FJ600, which, if you're interested in a little genealogy lesson, begat the '86 FZR600 and the '94 YZF600. Four years later, the YZF was soft enough around the edges to earn Best 600 GT in our August '98 issue. Brand-Y got serious again in '99, catching the rest of Japan Inc. on their corporate heels with the first YZF-R6. While initial rumors of 120 horsepower in a sub-400-pound package never materialized, the strategically recast R6 that materialized in the spring of '03 weighed an astounding 415 lbs. wet and made 105 horses at 12,750 rpm-11 lbs. and 9 bhp ahead of the '02 version. Credit a new aluminum frame and wheels for much of the weight loss. Factor in a stubby, 54.3-inch wheelbase and steering inputs are essentially instantaneous.
Inhaling through four 38mm vacuum-piston throttle bodies, the first fuel-injected R6 makes more midrange power than its carbureted predecessor. But racier '03 intake cams mean the engine isn't really open for business until the tach strikes 9000. It's serious business from there all the way to 13,000 rpm. Our testbike came with a dent in the power curve between 8000 and 9000 rpm that's only troublesome on the track.
Josh Ribbee, Warranty Adminis- trator at Cal Coast Motorsports in Ventura, California (www.cal coastmotorsports.com), says the R6 engine is fundamentally bulletproof. Valve adjustments are 26,000 miles apart, which is a plus. Water can work its way into some '03 ignition coils and cause rough running, in which case Yamaha will replace them. It's always a good idea to have a dealer run the VIN number to see what pops up, especially since some '03 R6s left the factory with insufficient torque on the countershaft sprocket nut.
It's a more comfortable streetbike than Honda's '03 CBR600RR, if somewhat less refined. Brakes deliver good power and better feel. The factory suspension setup is surprisingly good, but the 43mm Kayaba fork and piggyback-reservoir shock are happiest when firmed up to 35mm and 32mm of sag, respectively. The ostensibly unforgiving R6 ergonomics are actually quite kind to anyone over 6 feet tall. As a streetbike, any '03-'05 R6 is a better streetbike than the flashier third-generation version that broke cover in '06. Or Yamaha will sell you essentially the same bike as a brand-new '07 YZF-R6S for $8299.
New-for-'03 fuel injection is much better than carburetors. Plush suspension smoothes nasty pavement, and real-world amenities abound.
Shifting could be better. There's too much buffeting behind the windscreen at speed. What's with that dent in the power curve at 8500 rpm?
Notchy shifting. Rough running or lackluster acceleration from soggy ignition coils.
Quickness you can live with for a load less than buying new.
Kawasaki ZX-6R $5510 ('03)The 636cc Ninja makes 108 bhp at 12,750 rpm. It's 3 lbs. heavier than an equivalent R6 and takes more muscle to steer. Too-stiff stock suspension gets skittish on lumpy pavement. It's all about the engine on this one.
Honda CBR600F4i $4885 ('01)After surviving for years on the strength of its gracious, broadband demeanor, Honda finally dropped the F4i from its '07 lineup. A little scrupulous homework will save a bundle if you can learn to live with 95.5 rear-wheel horsepower.
Yamaha YZF600R $3415 ('97)You fly a bit slower on the original YZF600, and it's nearly 50 lbs. heavier than a '97 GSX-R600. Abandon delusions of track-day domination and put money in your pocket or buy a spanky new '07 version for $7099.