Editorial Note: This article was originally published in the January 2019 print issue of Roadracing World & Motorcycle Technology.

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By Chris Ulrich

There is something to be said about dedicated motorcyclists

designing, building, and developing motorcycles. The excitement of riding a

motorcycle is easy to describe to somebody who has done it, but hard to

transmit to most normal people: They just won’t get it unless they’ve ridden a

bike. KTM’s engineering staff is fully populated by riders, and that riding

culture comes through loud and clear with the 790 Duke. It is a case study in

building a motorcycle that is powerful, compact, and lightweight with sharp

handling, so it’s no wonder that KTM nicknamed it The Scalpel!



(Above) Roadracing World’s Chris Ulrich on the 2019 KTM 790 Duke, a middleweight streetbike combining a great power-to-weight ratio and sharp handling.



I could already tell it was going to be a good day when I clicked

into second gear and pulled out of the parking lot at the start of the official

intro for the KTM 790 Duke. The engine spun up through the rpm and ripped

through the gears effortlessly, and the day had just begun. We ventured out on

a route that took us from the Southern California beach town of Encinitas and

down the coast, then headed east towards Mount Palomar before heading back

toward the ocean. But it didn’t take a 150-mile loop on some of the best roads

Southern California has to offer for me to figure out that this KTM is a

ripping middleweight that will make anybody with a pulse want to get out and

ride!

The performance of the 799cc Parallel Twin engine really stood

out as we rolled down Pacific Coast Highway. Riding from stoplight to

stoplight, I couldn’t help launching off the line at each green and blasting

through the first three gears, before backing off to stay out of

speed-limit-related trouble. The 790 Duke gains rpm like a Superbike with a

lightweight kit stator, so quickly in fact that it gives the seat of the pants

impression of accelerating harder than its big brother, the 1290 Super­Duke R.

It’s a real-world example of a good power-to-weight ratio in two-wheeled

action!



(Above) Ulrich found the KTM also entertaining on the racetrack, although if we owned it, we’d upgrade the stock tires and front suspension.



The real fun began as we headed down Highland Valley Road and

made our way toward the east grade of Mount Palomar. Highland Valley Road is

tight, twisty and slick, and the 790 Duke showed its handling prowess without

making me take risks on the road. It delivers light steering and easy turn-in,

yet is stable at the apex, and finishes the corner well. The engine pulled out

of slow, second-gear corners effortlessly, and the 790 Duke also handled

faster, sweeping corners. I was so comfortable with the bike as we climbed the

hill that I kept catching myself going faster than anybody really should on an

open public road.

Carving up the twisty roads gave me a good idea of the 790 Duke’s

potential, but, as we always do, we took the 790 Duke out to the racetrack to

really test its limits. For that, I headed to a Fastrack Riders event at Auto

Club Speedway, which features a road course that is flat and a little bumpy,

but which also has a good mix of high- and low-speed corners that allow a rider

to really get a good idea of a bike’s capabilities.

Before getting into the details, let me say that the KTM 790 Duke

is fun to ride on the track. Not in a holy-smokes, rip-your-arms-out power-wheelie way. But in an

instant-power-across-a-broad-rpm-range way. The 435-degree firing order spreads

out the power pulses, delivering lots of tractable power from 4,000 rpm to

around 9,500 rpm. The power delivery is so smooth that I was able to turn off

the traction control for racetrack use—even with the standard tires—without any

drama. Accelerating out of the last corner and down the front straight at Auto

Club Speedway, the 790 gains rpm so quickly that I hit the rev limiter before I

knew it, and had to start anticipating my shift points. This is not a typical

middleweight!



(Above) The 790 Duke’s floating front discs with radial-mount calipers.

On the chassis side, the non-adjustable WP forks have relatively

lightweight springs biased toward street comfort, and they bottomed out during

very heavy, straight-line braking. When they weren’t down on the stops, the

forks offered reasonable control and feedback, and the stock 790 Duke was less

prone to tucking the front than its 1290 big brother, which may be due to what

feels like better weight distribution.

But this middleweight comes with a full selection of advanced

electronics. The combination of the Motor Slip Regulation engine-­braking

control system, the Quickshifter+ system’s auto-blip downshifting capability,

and the slip-assist back-torque-limiting clutch system improved braking

stability and helped keep the rear wheel in line at corner entry, even when the

front forks were on the bottom of their travel. Coming off the brakes and

turning into the corner is one of the KTM’s real strengths: The Parallel Twin

engine is light and compact, with the cylinders positioned nicely up front,

which reduces turning effort.

Once I was on my knee at the corner apex, the 790 Duke had good

feel and still finished the corner, even when I reached the traction limits of

the Maxxis Supermaxx ST front tire, buried the forks, and needed to correct

front-end slides. On exit, the 790 Duke rotated well through the middle of the

corner, which allowed me to get the gas open and drive out at full throttle.

And the rear tire gave decent feedback while spinning up during heavy

acceleration.



(Above) The 2019 KTM 790 Duke combines a steel-tube trellis-type frame and a die-cast aluminum-alloy swingarm with an open-lattice design.



Having said that, if I bought a 790 Duke and planned to do any

track riding with it at all, the first thing I would do is buy

higher-performance tires. The stock Maxxis tires may be designed for longevity

on the street, but just don’t deliver as much traction as I like. I’d upgrade

to a set of Dunlop Q3 or Q4 or Pirelli Rosso Corsa II tires for combined street

and track use, without needing to deal with tire warmers. I’d also upgrade to

heavier fork springs or just go straight to KTM’s optional WP Apex Pro 6500

track-use fork cartridge kit with springs.

My experience on the street and on the racetrack still made it

clear that the 790 Duke delivers, with good handling and a great engine,

setting a new performance standard in the middleweight Twins category. More

importantly, the bike is really fun to ride on the street and on the racetrack.

And after all, having fun is really why we all started riding motorcycles in

the first place!



Leading-Edge Tech In A Middleweight Package

The performance of the 790 Duke clearly illustrates how KTM has

established itself as one of the most progressive motorcycle companies in

business. Hard-core motorcycle enthusiasts are rampant in the ranks of KTM

employees, which may explain why the Austrian company keeps coming out with new

models that sell well. With the 790 Duke, KTM has positioned its latest naked

sportbike as a very capable bridge between the single-cylinder 390 and 690 Duke

models and the stomping twin-cylinder 1290cc Super Duke R.

It all comes down to packaging with the 790. KTM engineers wanted

to make the 790 as lightweight and compact as possible, so they chose to build

a 799cc DOHC Parallel Twin. The engine is so compact that it’s actually close

in overall dimensions to the company’s single-cylinder 390 engine. It’s

significantly smaller than the engines used in competing models like Yamaha’s

twin-cylinder FZ-07/MT-07 and three-cylinder FZ-09/MT-09 models, Suzuki’s

V-Twin SV650, and the BMW F-800 Inline Twin.



(Above) Assembled 790 engine.



To create the 790’s compact power unit, engineers started with

horizontally split cast engine cases cradling a one-piece forged crankshaft

with its rod journals offset 75-degrees. That allowed the engineers to set the

firing order at 435 degrees, producing the type of traction-enhancing

power-delivery characteristics typical of a V-Twin, but without the extra size

and weight of twice as many individual cylinders, cylinder heads, and valve

trains.



(Above) One-piece crankshaft with offset journals.

The engine has a bore and stroke of 88.0mm x 65.7mm and a

compression ratio of 12.7:1, and a set of lightweight forged pistons each ride

on a DLC-coated wrist pin carried by a fracture-split steel connecting rod.

Using the fracture-split technique for the connecting rod’s bolt-together

big-end creates a unique, more accurate and stronger self-indexing mating

surface, eliminating the need for locating dowels and thus reducing

reciprocating weight. The sleeveless aluminum cylinder bores are Nikasil plated

and the cylinder block features an open-deck design to help improve engine cooling.



(Above) Forged pistons and fracture-split connecting rods.



Four steel valves per cylinder are actuated by a set of

chain-driven camshafts combined with DLC-coated finger followers. A gear-driven

secondary balancer shaft is positioned between (and driven off) the camshafts,

while the main balancing shaft is placed low in the engine and is driven off

the crankshaft. The end product is a compact engine that put out a measured

98.26 bhp at 9,570 rpm and 59.16 lbs.-ft. of torque at 7,800 rpm on the Attack

Tuning Center’s rear-wheel dynamometer.



(Above) Attack Performance Center’s rear-wheel dyno showed the 790 Duke making 98.26 bhp at 9,570 rpm and 59.16 lbs.-ft. of torque at 7,800 rpm.

The engine is used as a stressed member in the chrome-moly

steel-tube trellis frame, helping reduce overall weight while also balancing

the flex characteristics of the chassis. The die-cast aluminum-alloy swingarm

is an open-lattice design that optimizes the balance between rigidity and flex.

Incorporating other parts of the chassis into the overall design, the

cast-aluminum sub-frame also houses the airbox, making room for increased

volume plus giving easier access to the air filter.

The advanced electronics suite includes lean-angle-sensitive

engine braking and traction control, controlled by a five-dimensional inertial

measurement unit (IMU) that reads yaw and roll movement and rate of change as

well as longitudinal, lateral, and vertical acceleration. The electronic Motor

Slip Regulation (MSR) system works with the power-assisted slipper clutch to

help prevent rear wheel hop and chatter on downshifts, and the MTC (Motorcycle

Traction Control) system comes with three pre-set levels and a configurable

fourth option. The Sport, Street and Rain settings offer differing levels of

traction control, with the Rain setting lowering the amount of power available;

all three MTC settings incorporate an anti-wheelie setting to help keep the

front wheel near the ground. The Track mode allows the rider to select five

additional levels of anti-spin that are less intrusive than the Sport setting

and to turn the anti-wheelie functionality off, and includes launch control for

racing starts. All the settings are easily accessed through the left handlebar

switch. The menu on the TFT dash is clear and making adjustments is fast and

easy. The dash also incorporates Bluetooth technology to allow the rider to

access music and manage phone calls—but why would they want to?



(Above) The KTM’s TFT dash is easier to read than most.

The 790 Duke follows the broad outlines of the other members of

the Duke family, with minimal bodywork, an upright seating position, and

tubular handlebars. Unlike more downmarket machines, the Dukes come with

more-sophisticated suspension components than usually seen in their market

segments. In this case, the 790 has non-adjustable 43 mm inverted WP forks with

progressive-rate springs that increase from 6Nm to 10Nm as they compress. A

single WP shock working with a progressive spring is located between the frame and

the swingarm. The forks feature an open-cartridge configuration with

compression and rebound functions located in separate fork legs, and also carry

progressive springs to help manage motion through a 5.5-inch stroke.



(Above) Exploded view of 790 Duke engine.

Front-wheel braking is handled by a pair of 300mm discs and

four-piston radial-mount calipers manufactured by JJuan, a Spanish brake

company. A single 240mm disc with a dual-piston caliper is used at the rear.

The bike comes with a Bosch ABS system which is remarkably sophisticated, offering

two different performance modes. The Cornering ABS setting is lean-sensitive,

assisting the rider in trail-braking into a corner by reducing the braking

force as lean angle increases. The Supermoto ABS setting allows the rider to

lock the rear wheel while maintaining ABS functionality at the front. In both

ABS modes, the intervention is smooth, not abrupt, giving the rider a natural,

comfortable feel at the brake lever.

The company claims a dry weight of 372.6 pounds for the 790 Duke;

measured on Roadracing World’s certified scales, it weighed 418 pounds with a

full tank of fuel. Weight distribution is 51.3% on the front wheel and 47.7% on

the rear wheel.

All in all, there’s a lot of technology and performance packed

into KTM’’s powerful and lightweight new middleweight. The 790 Duke is

available in showrooms now, at a suggested MSRP of $10,499.