It wasn't all that long ago when simply adding an aftermarket exhaust and carburetor jet kit (remember those?) to your sportbike quickly and easily netted you five to 10-and sometimes even more-horsepower. The stock exhausts were so restrictive that any aftermarket exhaust immediately required changing fueling, otherwise the lean condition resulting from the increased airflow could cause engine damage. And the stock mild steel exhaust was usually pretty heavy, meaning a lot of weight could be lost in the transition as well, adding even more performance.
Suspension was another area in need of help, and aftermarket companies were more than happy to oblige. The old damper rod/orifice system of damping was crude and antiquated, but it took the OEMs until the late '90s before they finally began using shim-stack/cartridge damping systems in the front forks of their sportbikes-and even those early editions were fairly primitive. A cottage industry of suspension specialists soon began, quickly growing into a well-developed and technology-driven market.
But as the constant onslaught of R&D has enabled the OE motorcycle manufacturers and their parts suppliers to create ever better products, the performance gains have been harder to come by. It's a natural progression; as the overall capabilities of sportbikes have climbed higher and higher, that envelope of improving performance has correspondingly shrunk as well.
I can recall when the first-gen Yamaha R1 made its debut in '98. Its performance was heralded as ground-breaking, but even more astounding were the results when we installed an aftermarket full exhaust on it. The R1 instantly picked up nearly 12 horsepower on top, along with a significant bump in midrange torque (which it already had in spades). And this was before we installed a jet kit; turns out that the stock R1 actually ran rich at higher rpm, which we theorize was Yamaha's way of ensuring that the cast mild steel EXUP valve collector didn't overheat. While the jet kit didn't result in any more gain on top-in fact, we kept the stock main jets-it did help smooth out the lower rpm ranges that were running a little lean due to the freer-flowing exhaust.
That type of easy horsepower gain can't be achieved anymore. The motorcycle manufacturers have gone through considerable R&D expense to ensure that the stock exhausts flow well enough to complement the rest of the engine and produce maximum power, all while staying within the required U.S. EPA and Euro III noise emissions standards-and this is with the now-required honeycomb catalyzers that are necessary to clean up the engine's exhaust outflow enough to pass those standards. In a motorcycle market where performance is the only measuring stick that really matters, the importance of maximum power hasn't been taken lightly by the manufacturers. With current sportbikes, you can realistically expect an average gain of three to five horsepower with an aftermarket full exhaust, even with dialed-in air/fuel ratios via a piggyback fuel computer.
The same is true to a certain extent with suspension. Stock OEM forks and shocks are light years ahead of their counterparts' performance from even 10 years ago. While the difference between stock and aftermarket performance isn't as close as it is with exhausts, the gulf between stock and modified suspension is smaller than it was in the past. With the majority of current sportbikes, upgrading the suspension is no longer the prerequisite it once was for any foray to the racetrack (racing is obviously a different story).
All that said, there is still a lot of untapped performance to be gained from aftermarket speed parts-it just takes much more technologically (and production) savvy companies to unleash that potential. For instance, manufacturers no longer need to go through the expense of installing different cams and exhausts for various markets; they now can adjust the power levels completely through ECU programming. This has given birth to a new aftermarket-the electronic speed purveyors. And it's one that surely will soon be growing.
The evolution of the suspension aftermarket has been similar. In the past, all you needed to do was build a shock with the same but slightly higher-quality components; that status quo won't work anymore. And the increasing sophistication of fork internals has whittled that market down to the few companies who have the tech and production capability to keep up with the rapid advancement in cartridge damping development.
Make no mistake, there's still a lot of unlocked performance in today's sportbikes. Just try to make sure you're exploiting the potential that's there before jumping in headfirst with modifications.