The biggest challenge to going fast on a high-horsepower motorcycle like the Hayabusa is putting power to the ground. Get on the gas hard and most times either the rear wheel spins up or you loft the front, both of which slow you down. Lowering the bike to keep the center of gravity as close to the ground as possible only goes so far to combat this problem. A longer swingarm may be just the ticket for your hard-launch dreams. Aftermarket companies such as Trac Dynamics sell swingarms in varying lengths (from stock to as much as 14 inches over, most adjustable), with prices starting at $995.
Swapping out the OE swinger for a six-inch stretched version is a fairly easy endeavor. Since you'll be taking off the rear suspension, you'll need a jack or a bike lift to support the bike's rear end after you remove the rear stand. A tie-down (or two) thrown over a rafter will act as a safety when attached to the back end. Remove the rear wheel. Removing the exhaust system's canisters and S-bends isn't necessary, but life is so much easier with them out of the way. Now focus your attention on the shock and linkage. Unbolt the bottom of the shock from the rocker. Remove the bolt securing the bottom of the tie rods. Rest the back of the swingarm on the floor while you extricate the pivot from the frame.
Although Trac Dynamics' swingarm ships with its own bearings, you'll need to extract at least one of the OE bearings to access the crush sleeve that resides inside the pivot between the two bearings. Remember, the moment you take that first whack at the bearing race, the bearing is junk. Never reuse bearings--buy new ones if your new swingarm doesn't already come with them. While you can go Neanderthal on the old bearing to get it out, heating the pivot with a propane torch makes the job of tapping out the bearing much easier. Once the pivot is heated, most mechanics are able to get the bearings out with a drift (or a flathead screwdriver) and a hammer--all without breaking a sweat. Insert the drift into the side of the swingarm pivot opposite from the bearing you want to press out. If you can't catch the lip of the inner race because of the internal spacer, a flathead screwdriver may help. With the drift on the inner race, give the bearing a whack or two until it moves slightly. Now switch to the other side of the bearing and repeat. Essentially, you are walking the bearing out of the hub. When the bearing pops out, set the crush sleeve aside for later.
Installing a new bearing is pretty simple. You can use a bearing driver set or a socket that has the same outer diameter as the bearing's outer race. If you're unable to find a suitable socket, you can always use the old bearing. The idea is to never tap directly on the bearing itself. To ease locating the bearing in the pivot, some mechanics will place the bearings in the freezer for a couple of hours. Others simply apply a little lubricant to the bearing. Tap the bearing until it is in the pivot flush with the outer edge. Slip the crush sleeve into the pivot and install the other bearing. Press the linkage bearings into place to give the tie rods something to pivot on.
Next, pack the bearings by pressing grease into the space between the rollers with your finger. Keep packing in the lube until you're sure the space behind the rollers is full. Press on the grease seals you took off the old swinger. Take the swingarm and slide it into the frame. Loosely assemble all the bolts for the swingarm pivot, tie rods and linkage. Torque the bolts to spec. Set the chain adjusters to hold the axle blocks in the appropriate position. Before you mount the wheel, you'll probably have to trim (or remove) the rear fender if your bike isn't already equipped with a fender eliminator. Now, mount the wheel.
Since the swingarm is significantly longer, you'll need to custom-cut your chain. Wrap the chain around the sprockets and mark where the ends meet. If you plan to dragrace in a class with a maximum wheelbase, set the wheel in position for that length and cut the chain one link shorter than the chain measures out. Street riders can simply cut the chain at the most convenient link. Don't forget to install a longer brake line before you practice your launches.
•Time: 1-2 hours
•Cost: $995
•Tools: Wrenches, sockets, torque wrench, front and rear stand, bike jack, hammer, drift, blowtorch, red thread lock, bearing grease, chain cutter/rivet tool
•Parts: Aftermarket swingarm, swingarm bearings (if required), longer rear brake line, longer chain
•Tip: Set your wheelbase before cutting the new chain
•Performance gain: Better traction for launches
•Complementary modifications: Install lowering links, lower front end and air shifter
•Contact information: Trac Dynamics, (661) 295-1956, www.tracdynamics.com
1: In order to remove the stock crush sleeve, tap out one of the bearings.
2: Some mechanics like to use red Loctite when installing new bearings. When it dries, the bearings will stay put.
3: Once you've installed the bearings, the new swingarm pops in the same way the old one came out. Now would be a good time to add lowering links.
4: To ease setup, measure and place the axle blocks before you mount the wheel. Note the clever block design: The front hole is for the first half of the six-inch adjustment range, while the rearward hole moves the wheel way back.
5: For bikes like the Hayabusa, removing the countershaft cover can be a real pain. By using a piece of welding wire, you can simply pull the new chain around the countershaft sprocket without removing the cover.
6: If you plan on using an air shifter, Trac Dynamics can build an air tank right into the swingarm.
7: Here's what a Hayabusa looks like with the extended swingarm set 5 inches over stock and the rear lowered four inches.