Kawasaki ZX-6R, Honda CBR600RR And Yamaha YZF-R6 - Maximum Middleweights

Josh Hayes' Erion Racing Formula Xtreme Honda CBR600RR
With numerous Formula Xtreme championships to its credit dating back to the mid-'90s when the class featured big-bore machinery, the Orange, California-based Erion Racing team knows a thing or two about building fast Hondas. In the hands of Aaron Gobert and '07 champion Josh Hayes, Erion CBR600RRs won all but a single Formula Xtreme race last year-an impressive record. Like the Attack Kawasaki, Erion combines HRC factory bits with the company's own products and select aftermarket parts for a potent end result.

The engine modifications include Pankl connecting rods, Erion/CP pistons, an Erion-ported head with HRC cams and valve springs, an HRC close-ratio transmission and an STM slipper clutch. The exhaust pipe is an HGA (Honda's R&D department in Japan) stainless steel unit, and a huge Febur radiator keeps things cool. A MoTeC ECU oversees operations, connected via a custom-built wiring harness. Similar to the system used on the Attack Kawasaki, the setup offers control of practically every parameter related to fuel and ignition, including traction control. "We utilize all those things to try and tailor it to any particular track or rider preference," says Rick Hobbs, technical director for the team, but all that adjustability comes with a price: "There aren't many things I can think of that it doesn't allow you to do. It gives you so many things that it can be detrimental sometimes because you spend a lot of time focusing on things that maybe don't make that much difference to the big picture."

The CBR's frame is stock, as is the swing-arm aside from the axle slots, which are enlarged to accept captive spacers. An Ohlins shock works the stock linkage out back, and up front an Ohlins fork is held by custom-made triple clamps. Interestingly, things like the triple clamps and rearsets are not adjustable; rather the parts are individually custom-made as needed.

Wheels are 16.5-inch forged magnesium Marchesinis with Dunlop slicks fitted. "We've been running mainly 16.5-inch wheels," Matt Zurbuchen says, Hayes' mechanic for the Formula Xtreme bike. "Most of [Dunlop's] development is going into 16.5-inch wheels for modified classes. They have a pretty good idea when we show up to the track what's going to work for a front tire. There's always a choice between two or three tires for the rear that may work, and we'll have to figure out what's going to work."

The CBR600RR was a new model for 2007, and while the Erion bikes were competitive right out of the box last year (aside from fuel problems that affected all the Hondas at Daytona) there was significant development time involved. "The bike in stock form is substantially better than the old bike," Hobbs reports, "but we had three years of development on the MEE [the part-number designation of the previous model] engine. So we had the new engine with a different cylinder head, cams, exhaust valves, springs, valve sizes and rod length, and it took us a little bit of time to get back to the level we were at with the older engine. Now we've exceeded where we were, but it took basically a season of development to figure out what we needed to do."

Interestingly, Hobbs notes that the new bike is easier to work on than the previous model. General maintenance is much easier, and the rear shock can be removed and replaced quicker. And because the swingarm pivot doesn't run through the crankcase as it does on the old model, dropping the engine from the chassis is simplified. "It's very well engineered, and reliability is, I think, one of the strong suits-knock on wood."

"[The chassis] seems to be a good baseline for whatever track we go to," Zurbuchen adds. "We're not making a mess of changes, front and rear wheel traction is always decent and we're not fighting chatter too much."

While the team is understandably cagey with numbers, we were told that horsepower is more than 20 percent over stock, which works out to approximately 130 rear-wheel horsepower by our calculations-and we're sure that's a pretty conservative number, judging by the bike's performance on track. The CBR is within a few pounds of the minimum weight for the class, and with a titanium pipe replacing the stainless steel unit for 2008 Hobbs expects to be even closer to the minimum. "It was pretty easy [to reach the minimum weight]. Last year we had a stainless steel exhaust and no titanium to speak of. The wheels are about the trickest weight-saving part on the bike."

"Hate to use this clich," Kento says after riding the Hayes CBR, "but it was a typical Honda with a well-sorted suspension and chassis, and it never wanted to do anything unruly, while giving you tons of feedback from the tires. The motor was much smoother than the Kawasaki but didn't quite have the screaming top end, with power starting to taper off just a bit past 15,500 rpm; nonetheless it's unbelievably quick for a 600 and felt like it would stomp a stock literbike." Bystanders could clearly hear the Honda's traction control kicking in when the bike was on the track, but Kunitsugu reports he could neither hear nor feel the engine missing and the Honda had smooth throttle response and came off the corners easier than the other bikes.

Of the three bikes we sampled the Honda was set up the softest and the easiest to ride on Buttonwillow's bumpy surface. "I loved the chassis," Kunitsugu wrote in his notes. "It has the same nice feel as the stock Honda in the corners, especially during turn-in and while really pressing the chassis/suspension at the corner apex. It had a 'friendly' feel that didn't give me the impression that it could spit me off at any time, which obviously bolsters confidence. Suspension rates were probably the most suited to my speed and riding style and handled some of Buttonwillow's bigger bumps the best of the trio."