Over the last decade or so, the evolution of sportbike design has advanced so much that it makes it challenging for some of us to do the necessary modifications at home. So rather than scream cuss words while fumbling around the garage, we enlisted the savvy of Jett Tuning, a Southern California-based motorcycle performance shop.
Due to a riding mishap I had at the track earlier in the year I handed over the CBR already crashed. (Hey, at least I got it out of the way). Fortunately, it was a simple low slide tip-over and the bike didn’t roll or flip so the damage was minimal aside from bodywork and controls.
After peeling away the scraped fairings, Jett replaced some of the broken hard parts. New clip-on style handlebars and foot controls were sourced from LighTech (distributed by Canadian company OPP Racing). The components are fabricated from aluminum and feature an anodized black coating. The rearsets also offer full adjustment in terms of footpeg position and brake and shift lever length and height. We also installed LighTech frame sliders, swingarm spools, and chain adjusters, plus a red anodized steering stem nut just for some extra bling. New adjustable front brake and clutch levers were sourced from CRG while a tacky set of Renthal Road Race Full Diamond Grips were fitted onto the bars.
Although the stock Showa suspension performs adequately at a track day pace, when you’re hanging it all on the line during a race it’s key to have the proper spring rates and suspension valving based on your weight and/or riding level/skill. Having heard great things about Georgia-based suspension tuner, Traxxion Dynamics, we sent off the fork for service.
Traxxion Dynamics fitted heavier fork springs as well as its gas-charged cartridge fork kit designed for racing.
Traxxion swapped the OE progressive coil springs for a pair of constant-rate springs (0.975 kg) according to my weight (180 pounds). It also fitted its proprietary AK-GAS cartridge kit. The set-up consists of a pair of pressurized and gas charged cartridges allowing for more consistent damping control. The $1999 kit retains the stock fork tubes which makes it legal for competition in virtually all race series.
Out back, Jett replaced the OEM Showa shock for a unit from JRi. The aftermarket piece is assembled in North Carolina utilizing an all-aluminum body with a piggyback-style gas-charged reservoir. It offers four-way adjustment for spring preload, high-and-low-speed compression and rebound damping. Furthermore it also has a built-in ride height adjuster. JRI fitted a 10.7 kg steel shock spring, again based on my weight.
Although production racing limits the modifications you can do to many components including the brakes, there are still some cost-effective improvements to be had. We started by replacing the front discs with a pair of Galfer Front Wave Rotors. The discs are the same diameter as stock (310mm) but 0.5mm thicker for better durability. The rotors were paired with race-only carbon ceramic brakes pads, which enhance stopping power and feel at the lever. Since we’re only going to be competing in production-classes the original Tokico calipers had to be retained however they are augmented through Galfer Colored Sport Bike Brake Lines front and rear.
One of the most expensive aspects of racing can be engine building with aftermarket go-fast parts, including pistons, cams, etc. So instead of trying to spend lots of money with internal motor upgrades we opted to try and squeeze the most amount of power out of the stock engine. First, we ditched the restrictive stock pipe for a Yoshimura RS-5 Exhaust System (stainless-steel header/mid-pipe and carbon fiber muffler).
The Yoshimura RS-5 exhaust added power, reduced weight and helped make the bike faster on the dyno.
While the CBR’s fuel-injection system is capable of compensating for the added exhaust gas flow we wanted to have the ability to adjust the bike’s fuel and ignition timing curves, as well as the sensitivity and response of the throttle. To do that we plugged in a Dynojet Power Commander V with optional Dynojet Quick Shifter Expansion Module. The add-on component allows for immediate, seamless gear upshifts thereby saving precious time on the stopwatch. The great thing about Dynojet’s Power Commander is that it has a variety of maps you can download of its website based on the type of exhaust system on your motorcycle. However since the maps are built for the masses compromises have to be met. That’s why for maximum performance it’s a good idea to build a custom-map. And that’s where owner, John Ethell’s years of top-level AMA racing and racebike assembly experience comes into play.
Ethell spent about 2.5 hours on his in-house Dynojet 250i dynamometer creating a map for the Yosh pipe as well as the type of race fuel we were going to race on (VP Racing Fuels MR12). All said and done Ethel was able to extract 14.8 additional peak horsepower (119.03 total) at 14,100 rpm (1300 higher as compared to stock). Peak torque was also increased by 2.76 lb-ft at 11,500 rpm (300 higher than stock). While more top-end power is always good what’s really impressive is the increase in horsepower and torque throughout the powerband once the engine is spinning over 5000 revs. Also of note is the big improvement in over-rev with the engine pulling longer and harder before the rev-limiter shuts the engine down at 15,500 rpm.
(Above) With the fitment of a Yoshimura RS-5 exhaust system and VP Racing Fuels MR12 race gas our CBR600RR produced almost 14% more horsepower compared to stock. (Below) We had Escondido, California’s MC Pro Designs paint our racebike in the same color scheme as a 2012 production bike at a cost of $750, without the fuel tank.
Next up was to source bodywork. It just so happened that our friend, John Hensley, had a brand-new set of Sharkskinz fairings gathering dust in his garage. Fortunately, Hensley’s set included the race-style tail section that replaces the squishy stock seat for thinner foam seat pad. Although the foam pad is less comfortable it enhances the rider’s feel of the road, tire and shock. We also invested in a Zero Gravity Double Bubble Windscreen thereby enhancing the aerodynamics of the motorcycle as well as creating more room for larger rider’s to tuck out of wind blast. Once we got the bodywork fitted we dropped it off at MC Pro Designs in Escondido, California where it replicated the 2012 CBR600RR’s original paint scheme.
Stay tuned for the following part of our CBR600RR project bike story in which we test each of the modifications by competing at Southern California’s Auto Club Speedway to with America’s oldest road racing series: WERA Motorcycle Racing Club.
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