Harley Davidson FXDB Sturgis

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Harley-Davidson FXB 1340 Low Rider Sturgis

Rit Booth carries a long Harley-Davidson Program Manager for Big-Twin Sport Bikes. The M.I.T.-trained engineer is heart-… about motorcycles, and like of Harley’s young technical is enamored with performance. One of his machines is an XR1000 modified beyond recognition.

Society of Engineers monographs on motorcycle bear his name, and he’s as pushing bits in computer as he is twisting a throttle.

Yet any discussion Booth about the project filled the last few years of his life, the project that has Harley’s newest Big Twin, the that has revived the Sturgis any such discussion revolves one, and only one topic: The Look.

The Motor Company in the business of quick, or fast, or H-D’s in the image business. that doesn’t mean is treated as a bastard son, The Look a Harley seems as of purpose as George Hamilton a tan.

After years of the company has The Look down about perfect. For proof, we the 1991 FXDB Sturgis, a resurrected from Harley’s now affixed to its most radically motorcycle since the Evolution in In H-D’s lexicon, the FXDB as all-new.

Cynics may snort this description usually the company has simply reshuffled parts, bolting up a new model as much substance as the emperor’s new

Thumbing the Sturgis’ engine to gives the first indication there’s more than to this bike. As it chuffs at idle, the quality of the vibration from other rubber-mounted — still pronounced, but the isn’t trying to jump from its mounts, as it seems on the for example. Running through the confirms there’s something about this Harley.

The peaks at idle, and from to redline it tapers off dramatically as climb; at highway speeds the vibrates less than four-cylinders. Roll off the throttle at any and the bike becomes eerily

Maintaining The Look, though, that when this new is parked, only a dedicated is likely to pick up the subtle to its new character. The blacked-out engine, black paint, H-D orange and minor chrome accents are all lifts from the FXB Sturgis of 10 ago, and its new namesake seems paint-and-tape away from or four models in the current

The sharp-eyed will notice the seems less cluttered, tightly and neatly packaged. The of a traditional oil tank seems the thing out of the ordinary.

Plenty of parts link the with the current line-up. The uses the standard 80-cubic-inch, V-twin, backed by a five-speed duplex-chain primary and belt drive. Similarly, the fork, shocks, instruments, and many bits have seen elsewhere in Milwaukee’s line-up.

the cynics can curl their around the words parts-bin however, remember that components are H-D’s basic blocks, and the company’s used parts to fashion itself the maker of the best-selling large-displacement Booth notes that from scratch places demands on design and testing, and he saw reason to reinvent the wheel in the Sturgis. Besides, it would be the point to claim the FXDB is more than a parts-bin nature built Michelle and a garden slug out of the same but no one’s going to claim little difference between the

Booth and Co. are entitled to a bit of hyperbole, given that they’ve got the definitive cruiser power-plant. who’s pulled the wire on a V-twin knows there’s indefinably visceral about the delivery. The power starts at and is always there, regardless of The bike never drops 55 pound-feet of torque from to redline, and its torque peak, pound-feet, occurs at 3000

At 3500 rpm, the Sturgis’ cruising speed, it’s 11 pound-feet and 7 horsepower more a ZX-11. This kind of elephant power delivery is the stock in trade. When you to 20 mph in top gear and then simply on the throttle to shudder away, no denying its appeal.

Even the basic driveline comes the company’s FX series, it’s not a lift. The engine bolts to a of new castings, including a primary that moves the engine slightly, and rotates the cylinders 4 back in the frame compared to the FXR. (Softails mount engines so that a vertical bisects the angle between the FXRs mount theirs this bisecting line forward 2 degrees.) The re-angled provides additional clearance the steering head, which the engine and transmission assembly to forward in the frame. The additional on the front wheel improves stability.

In addition, the Sturgis the long primary case the FXST Softail, which an inch farther, crank to clutch center, than the FXR The reason, Booth notes, back to the heart of the matter: part of what gives it the by making it look longer you it look lower. Longer and are two main components of The Look.

The added driveline length provides room for the oil tank, has been incorporated into a new below the transmission, so that it much like the sump on an This rids the bike of the lines twining between the oil and tank, for a more sanitary The design simplifies manufacturing as by eliminating the oil lines running the engine and the frame-mounted oil tank, the can slip the complete engine into the chassis pre-plumbed.

accentuating the length, the DB uses a 32-degree rake. Moreover, bolted up a long fork inches, compared to 31.6 for the one), and grafted an additional into the swing arm. As a the Sturgis puts 65.0 of real estate between its longer than anything in the H-D pantheon save the Softail and Custom.

Achieving The Look a lot of territory.

The real news, lies between those The FXDB takes its modified Big driveline and bolts it into a rethought chassis, and it’s that earns the bike the to be considered all-new. The revised includes a new frame, swing and reworked engine mounts.

more, the Sturgis raises the aspects of H-D’s customs to a new in most ways surpassing the existing decathlon champ, the

All this work centers on one aspect of the FXDB: engine When the system used on Big Twins was devised in the mid- to the company designed its frames existing technology. The engine Harley adapted to its own use were or less off-the-shelf automotive basically a bolt surrounded by a rubber biscuit.

The original involved a number of compromises, with the necessity to use three mounts—one in front, two in the rear to the entire engine/swingarm/rear-wheel unit, a pair of heim-jointed turnbuckles to prevent torsional or side-to-side that would destroy alignment and handling. The system movement in one vertical plane without chain pull vibration isolation. Within defined parameters, the engine was to move front to rear or up and but not side to side.

The design but the triple-rubber-mount system made the relatively wide, since the frame rails had to reach the rear rubber mounts, sat outboard of the engine and swing In addition, the rear rubber helped locate the rear of the package, and their side-to-side depended on how much they preloaded—which also affected how they absorbed vibration. The almost guaranteed some variation in vibration control.

With the new bike, Booth he was looking for something simpler. We want to build the bike the rubber mounts. [With the old we took the old mounts and packaged a around them. To replace the parts, he used a pair of mounts of alternating rubber and A pair of steel plates a metal block between rubber pads; the steel bolt to the engine and the center bolts to the frame.

Helicopters use a system to mount the rotor

Figuring the basic configuration of the was only part of the solution. It to to determine the stiffness of the mounts, to locate them, and even how to what better and best in terms of vibration control. was uncharted territory—so new that the FXR engine mounts gave no as to a starting point.

Booth, by a computer, had to sort through than 46,000 potential

The new system works because the new offer stiffness that with direction: soft and in the vertical plane to absorb stiff laterally to keep the wheel in line. One of the two rubber snuggles under the front of the the other attaches at the back, the transmission; both reside on the centerline.

The two new mounts locate the of the engine, while a single resides between the cylinders to the engine’s top, and prevent any out-of-plane movement. Compared to the one turnbuckle and one mount is missing.

The does exactly what supposed to do for the rider: Overall, is the smoothest Harley yet. The new snub vibration differently—if not better—than the old system. At idle, the big V-twin leaps about than an FXR engine, for a more if slightly sharper-edged feel.

At 35 mph to 45 mph in top the Sturgis passes slightly vibration through to its rider an FXR, though relief is a downshift away. At higher or engine speeds, vibration disappears; the view through the is clear, even though you can light, reassuring torque from the big Milwaukee powerplant. On the FXR, the rubber mounts lose control as the engine redline, but at high speed the keeps buzziness under rein.

The system also Harley to change the bike’s particularly the aft section. The widely frame rails that around the swing arm on the FXRS are on the Sturgis, as are the exposed rails run up to the seat. Instead, the big, rectangular-section backbone (which at the seatbase on the FXR) curves ending just above the and a pair of closely spaced tubes snake up from to support the seat and shocks.

Nary an inch of round is visible behind the engine.

In the stiffer new mounts limit movement. Whereas the earlier system allowed for as much as an of engine/transmission excursion, the new arrangement that approximately in half—a cut was vital for this latest of The Look. Harley’s designers to pack the engine closer to components, as on the Softails with rigidly mounted engines.

in the existing FXR’s driveline this, which gives Glides a less tidy than Softails and their The new mounts solve that

Booth considers frame to be one of the current FXR’s best and wasn’t about to risk any of that for the sake of either control or The Look. Frame is hefty. The rectangular-section backbone is from 0.120-inch thick and now works with with new castings and forgings. The steering is an investment casting, which the fine detail necessary to the new steering-head lock a drop-in

The bridge for the swing arm is a steel while the engine-mount plates are forged.

On each part we at the best process. We’ve come at each one without any ideas of what each one be. We used a mix of stamped parts, a lot of Booth notes.

Here the new bike is at least the equal of the Hard braking or cornering to bring out any hint of wobbling or Granted, with less 53 horsepower on tap and only a single up front, the FXDB isn’t to put race-level stresses through its but it still seems massively another facet of The Look.

city limits, the Sturgis supreme. The riding position a near-perfect balance between the slouch and the FXRS Sport A set of risers moves the Sport-style up 4 inches and back about 2.5 and places the grips an easy from the saddle. The engine, the Keihin CV carburetor now used on all engines, starts easily, strongly and smoothly from than 2000 rpm, and with low-speed torque.

The new that all Big Twins share year requires less effort, and disengages more With less clutch the transmission shifts more though it still requires a lever throw, and gears engage with a clunk but a one. Turn signals from the FL Ultra Classic models no longer flash when their control are held down; push and a signal flashes until a decides long enough, or you push again.

The Sturgis comes with the stock seat ever on a Harley custom it’s flat, and thick enough to all-day comfort. Unlike FXR perches, it features a smooth, cover instead of the usual button-tufted covers. More it doesn’t lock you into a position, and for most riders puts the highway pegs easy reach.

Above 60 mph will make you wish for a bit rise from the handlebar, or for a bag to lean against, but up to that this is hands down the comfortable Harley custom built.

Only a few detractions — and they’re in areas styling and function inevitably paths. The fork provides a harsh ride — because the 32-degree rake it out too far to work optimally. The rear though, is far worse.

The shocks an abundance of preload and a dearth of damping. Rolling dips, as suburban rain gutters, to fling the rider’s … out of the and any abrupt-edged imperfections come with the sharpness of a rifle

Why? Because The Look, and traditional customers, demand a low machine with a seat to the ground — and that compromising either traditional sizes or suspension travel. The runs a classic 16-inch wheel, but allows it to move 3.0 inches — not enough to the edge off most bumps.

and his team have mounted springs with substantial in an effort to make the best of a bad but in the end that approach by making out more likely only matters worse on big bumps.

To any misinterpretation of the bike’s non-sporting Harley left a second disc on the parts shelf. a message to [the single This isn’t a sport Booth says. But, again, The Look and function are at The Sturgis’ front brake an unusually firm grip, and unsatisfying feedback. The bike better.

If it must use a single it should be a bigger one clamped by a sophisticated caliper, and with leverage ratios.

Similarly, the so pleasant in town or on the highway, like being hurried. redline, the big V-twin loses of its charisma, and it’s easy to the low-revving powerplant off its 5200-rpm The transmission also shows enthusiasm for sport riding, balky and refusing to change cleanly when shifts are

While the Sturgis wasn’t with backroad sport in it can handle curves surprisingly The locomotive-class wheelbase, stout and conservative geometry keep the locked on trajectory in a corner, nothing but the most reassuringly feel coming back the bars.

Despite remarkably cornering clearance (kick-stand and case touch down on the front muffler on the right, the bike has leaned only more than 30 degrees) the handles well. Lots of and trail slow its steering, but the handlebar keeps effort low.

For normal, don’t-push-the-limits this happens to be the best custom yet. The Sturgis day-today living as competently as an Sport, yet the new chassis gives it a broader operating range. In its for The Look, Harley managed to function as well; in the Sturgis the two are together as neatly and thoroughly as the of a rope.

Best of all, the is only the beginning. This is intended as a commemorative model of marking the 50th anniversary of the Hills rally and the 10th of the bike’s namesake. But the new chassis can be easily adapted to other Big models, some that have more suspension and a less rakish steering angle. The Sturgis engine also provide hope for seeing a rubber-mounted Sportster.

The engine-to-component spacing of the Sturgis far from XL practice, and the design can be relatively easily to that

This is the most significant to come out in almost a decade. The FXRS in 1982 qualified as the important new Harley in a generation. It what Milwaukee could do it combined the company’s traditional with modern engineering: the styling without losing

The 1991 Sturgis does bike one better; without The Look, it takes function one further.

Source Cycle 1991

Harley-Davidson FXB 1340 Low Rider Sturgis
Harley-Davidson FXB 1340 Low Rider Sturgis

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