While the engine was at Hypercycle, the rest of the chassis was dropped off at friend-of-SR Eric Nugent's garage, and our Geek made the phone calls and sent the e-mails to round up the necessary bits. Nugent built our last project racebike, an '04 Suzuki GSX-R600 that Corey Neuer raced in 2005 ("The FX Project," Jul. '05, and "Scared Straight," Aug. '05), and was a huge help in bringing this project to fruition. As expected, the availability of aftermarket parts for the 675 is not as extensive as it is for a typical Japanese middleweight, and in many cases the options for parts are severely limited. Still, we gathered up an impressive stash of speed parts for the bike, and all the companies we dealt with expressed enthusiasm for the project and the bike itself.
The kit camshafts have the...
The kit camshafts have the same lift as stock (as required by World Supersport and AMA Formula Xtreme rules) but more duration. Slotted camshafts allow timing to be changed, and a manual cam-chain tensioner replaces the stock hydraulic unit.
The kit wiring harness eliminates...
The kit wiring harness eliminates the extraneous street gear. Not only is the harness itself more than 1.5 pounds lighter than stock, it allows the ignition switch, left handlebar switch and other street-oriented bits to be jettisoned. The kit ECU raises redline by 1000 rpm and has provisions for a quickshifter to be wired in.
The valves included in the...
The valves included in the kit (the left of each pair shown here) are flat-faced to increase compression slightly. The stock valves are a two-piece design, while the kit parts appear to be one-piece. The heads on the kit valves are thinner and have a shallower dish, offsetting the additional weight of the flat faces-the kit valves are each about one gram lighter than the stock parts (22.5g versus 23.7g intake, 21.5g versus 22.3g exhaust).
Two thicknesses of head gaskets...
Two thicknesses of head gaskets are available in 0.5mm increments thinner than stock. We ended up using the stock head gasket to meet the kit manual's guidelines for squish clearance.
The kit valve springs (left)...
The kit valve springs (left) are shorter and made from a thicker wire than the stock springs (right). The ends are ground so as not to wear the retainers.
Halfway through the project...
Halfway through the project Triumph issued new springs (right) that appear to be made of a different material from the original kit bits (left).
With the engine complete and the chassis parts obtained, the bike came together in Nugent's garage, and we ventured to Auto Club Speedway (formerly California Speedway) in Fontana for a track day. Local club racer John Reeves volunteered to be the guinea pig and reported stable handling, good steering manners and power on par with a well-prepped supersport machine. We had just a couple of stumbling blocks during the day: The kit charging system only works at high rpm, and with the stock battery we needed to keep a charger hooked up when the bike wasn't being ridden. And fitting the switch for the quickshifter proved very difficult with the Woodcraft rearsets-there is barely enough room between the shift shaft and the frame. We eventually squeezed everything in, but our Power Commander was shipped with the wrong software to activate the quickshifter, requiring a call to Dynojet to obtain the right code.
It ain't pretty, but it works....
It ain't pretty, but it works. We were worried about running out of ride-height adjustment with the huge rear Pirelli slick, so we installed this lowering link from Adjustment Tech Racing ($280). There have been reports of the linkage bolts pulling out of the plates (with the expected consequences), so Nugent carved a second set from aluminum plate to add some support. The plates' unequal dimensions mean they can be oriented in different ways and used with a longer dogbone to subtly change the rear-suspension rate.
Woodcraft rearsets are the...
Woodcraft rearsets are the company's typical high-quality affair, with billet parts and three-piece pedals that make crash repair easy and cost-efficient. The 675 kit with GP shift retails for $399, and the footpegs and pedals are adjustable using this nifty pin arrangement (inset). What's not shown here is the Woodcraft setup for reverse shifting, which consists of a double linkage to put the rod through the frame in the original layout. The setup leaves no room for a quickshifter switch, and with the stock transmission internals (the kit parts smooth shifting substantially) it was impossible to make easy shifts. Nugent drilled a hole in the bracket to mount the stock shift pedal so we could run the rod and switch outside the frame.
The forged-magnesium Marvic...
The forged-magnesium Marvic rear wheel is six inches wide and allows the latest Pirelli 16.5-inch slicks to be fitted. Renthal supplied us with all our gearing needs. The company's front sprockets ($50) are CNC-machined from steel, case-hardened and drilled for lightness, while the rears ($83, available through T.A.W. Vehicle Concepts) are manufactured from 7075-T6 aluminum and hard-anodized. The RR4 chain ($175) is a high-strength, lightweight, 520 sealed-ring version intended for racing applications and is prestretched.