MO has had the KTM 790 Duke in its collective possession for almost seven months, and weâve gotten to know it pretty well. So, we knew the time was ripe for a follow up to my First Ride Review. However, I was concerned that writing the update would remind the folks at KTM that we still had their bike and prompt them to ask for it back, which would make me very unhappy. So, I came up with a plan, and it seems to be working.
The 790 would become a project bike, making it necessary to keep the Duke in our stable for as long as possible. Weâll start with our modifications the way many new bike owners do, by installing factory accessory parts before branching out into the aftermarket in future installments. Thatâs the plan, and weâre sticking to it â at least until KTM demands their bike back.Â
The 790 Duke has acquainted itself quite well to the varieties of chores itâs been given. In commuter mode, it has proven to be a worthy weapon for scything its way through the worst traffic that Los Angeles has to offer. On interstate highways, it is a handful â but not in the way I thought it might be. The engineâs smoothness frequently puts me in the position of accidentally going way too fast. Get-pretty-silver-bracelets-fast. Frequently, I look down at the TFT screen to discover that Iâm going between 90 and 95 mph. It boggles my mind that Iâm on a naked bike with no form of wind protection, and yet, Iâm not aware that Iâm hauling ass. Itâs crazy.Â
A great starting point with only a couple items that really screamed out to be changed. (Photo by Simon Cudby.)
The engine is a huge part of what I love about the Duke. Yes, I am extremely partial to parallel-twins because of their narrowness and my personal history with them. However, the physical configuration is only part of the magic. The 75-degree offset of the crankpins combine with a 435-degree firing order to approximate the feeling of KTMâs bigger 75-degree V-Twins. Add to that V-Twin character the most seductive power delivery I can remember, and youâve got a good time on your hands. Yes, a 1290 Super Duke R can eat the 790 for lunch, but its engine is so powerful that you really canât pull its tail for anything more than a few seconds on the street. With the 790, you can enjoy more extended runs into the top of the power band, snicking your way through the gears. And the smoothness enabled by the dual counterbalancers canât be understated. Those Austrian engine designers know what theyâre doing.Â
Rereading the above paragraph, I feel I need to clarify about engine vibration. Any parallel-Twin will vibrate in the upper rpm range, and the 790 is no different. Wring its neck, banging shifts right around redline, and youâll notice that the grips and pegs do vibrate. Just not as much as with other parallel-Twins. Drop the tachometer down to the mid-range, and the Duke gets unbelievably smooth. Thatâs whatâs gonna get me in trouble if Iâm not careful.Â
Whether youâre riding around town, hauling down the highway, scratching in the canyons, or strafing apexes at the track, the KTM 790 Duke is versatile enough to make any activity an event.
So, what about the quirk I mentioned in my initial review? The failed upshifts I encountered on my introductory ride have not been an issue. First, I have to say that those problems were encountered on a different loaner bike. When our first 790 developed a strange top end knock, KTM asked us to swap bikes before our comparison with the Triumph Street Triple R (and we obliged them), and this Duke hasnât suffered from either the shifting or rattling issue. However, I have spent enough time haunting 790 forums and Facebook groups to know that my missed shifts with the first 790 werenât a completely isolated experience. While the symptoms for me were missed shifts (the quickshifter cut the power, but the transmission stayed in the same gear), more people appear to have an issue with false neutrals. I donât think this is super common, but it is out there. Still, I think I can count on one hand the number of times Iâve missed a shift on this particular 790.Â
When it comes to the auto-blip downshifts, I have to say that the 790 has grown on me. I donât know if Iâm doing something different, but Iâm much happier with the quickshifter now. I use it constantly â both around town in traffic and when railing through the canyons. The shift from first to second requires some technique, but once mastered, the shifts are butter-smooth. The trick in traffic is to short-shift, and you can change gears at neutral throttle. Otherwise, you need to be accelerating smartly. The downshifts simply work.Â
One problem that cropped up at about 1,300 miles is that the countershaft seal started to leak. At first, it just looked like excess chain lube seeping under the countershaft sprocket cover, but as the leak progressed, it became clear that the problem was an oil seal. The fix is pretty simple for a mechanic of average skills. Still, weâre waiting to have it done the next time we take the bike to be serviced. We just keep the engine clean and check the oil level frequently.Â
Once I removed the countershaft cover, it was plain to see that the oil coating the engine came from the countershaft seal and not excess chain lube.
An electronic oddity that we have noticed is that every time the ignition is turned on â even when the tank is low on gas â it reads as two bars from full. After a few miles, the fuel level reads normally. This has caught me out a couple of times, but Iâve found that range readout is always accurate. So, I always check it when I first get on the bike.Â
Back home after a day on the track at Buttonwillow, this sight greeted me when I began unloading the bike from my truck. Yes, itâs coolant.
Another glitch I encountered with the 790 came just this week after a trip to Buttonwillow with Cali Track Days. The cooling system leaked on the way home. Although I havenât confirmed the issue, I suspect one of the hose connections to the radiator is the culprit. This will be addressed in our next service at KTM.
The 790âs speedometer reads on the high side. I checked it against the GPS on my phone and found it to be 4-5 mph over the actual speed at 80 mph. Thatâs ok. I can do simple math and ride at the same time when I see a black and white in the vicinity.Â
A few non-sequiturs: The speedometer jumps into night mode very easily sometimes from something as simple as riding through the shadow from a tree. However, it doesnât switch back to day mode as quickly. Iâm guessing that this is a safety feature for night riding where the day mode could throw glare into the riderâs eyes, say if you rode under a street light. When night riding, I really like the backlit buttons on the switchgear. The turn signal switch is in an awkward position, causing me to occasionally have a hard time signaling a left turn. The coolant expansion tankâs level check window is just about useless. Weâve averaged 39.3 mpg over the length of our possession of the Duke. (This excludes track days because we pour gas directly from a can into the bike.)
Stage 1 of our KTM 790 Duke project in track trim (shorn of mirrors and brake light/rear turn signals).
Many riders buy their first mods for their motorcycle at the time of the bike purchase so that they can tack the parts onto the bike loan. Consequently, their first changes are usually found in the manufacturerâs accessory catalog. I spent a lot of time on the KTM website, shopping out the PowerParts that I thought would most suit the bike and ended up with what I consider to be a fairly typical selection of KTMâs accessories.Â
In my opinion, the biggest stylistic warts on the 790 Duke are the passenger pegs and the hangers that hold them in place. So, I ordered up the Silencer Bracket ($78) to hold the pipe in place without the right side passenger peg. While I was planning to toss the pegs (and save 3.8 lbs., by the way), I figured the pillion should go, too. Next came the Pillion Seat Cover ($125), which completely replaces the passenger seat.Â
If youâre on a budget, the Silencer Bracket and the Pillion Seat Cover are a nice way to make the 790 Duke look sportier and shave off a total of 5.6 lb.
Installing the silencer bracket took maybe 15 minutes. On the left side, the peg-mount was removed and shorter bolts torqued in place to the specifications included in the kit instructions. On the right, the muffler had to be mostly removed before the peg bracket could escape. In short, a total of five bolts had to be removed and replaced. Easy-peasy.Â
The pillion cover took a good bit longer because it didnât come with the bolts to secure the rear pad to the cover. Iâd expect better from an OEM part. So, 20 minutes and $2 later, the pad was secured with a pair of stainless steel bolts and washers. (Oh, how I love my local hardware store.) I also had to mount the orange stickers on the sides. No biggie. The Pillion Seat Cover cuts another 1.8 lb.
The KTM PowerParts Fly Screen ($89) arrived from backorder just before I posted this article. I selected it because it completes the swoopy lines of the headlight and covers the blocky shape of the instrument cluster. I didn’t expect it to have much of an influence on the wind blast, but I was pleasantly surprised at how it smoothed the air hitting my chest.
While the ease of installation and the quality of the Silencer Bracket was exactly what Iâd expect, the Pillion Seat Cover seems cheaply made. Yes, its style perfectly matches the rest of the bike when viewed from a distance. A close inspection, however, reveals some inconsistencies in the surface from the injection molding process. Still, it earns a B while the exhaust bracket is a solid A. The back of the Duke is transformed with the addition of just these two parts. Also, if youâre not interested in replacing the muffler, the shapely stock muffler looks much better when it is no longer obstructed by the passenger peg.Â
The next item to get installed was the AkropoviÄ âSlip-On Lineâ ($860) from the KTM PowerParts catalog. Even if the passenger peg were still on the bike, this modification is just a two bolt operation. Remove one bolt on the muffler and the one on the strap that connects the expansion chamber/catalytic converter to the muffler then wiggle the stocker free. The AkropoviÄ goes back on just as easily. After you torque the bolts down, wipe the entire slip-on with a clean cloth so that you donât burn your finger marks into the pretty titanium of the canister when you fire the engine up.Â
The AkropoviÄ looks and sounds so sexy on the 790. Too bad it didnât add any power. Perhaps, thatâs the price you pay for all the baffling required for 50-state legality.
What a sweet sound this 50 state, EPA-legal slip-on puts out. No, itâs not much louder than stock, but the note is deep, resonant, and quite pleasing to my ear. Iâm not a huge fan of loud pipes on the street, and I think the AkropoviÄ does a great job of balancing the exhaust note we crave with consideration of those around us.Â
The AkropoviÄ slip-onâs power curve almost exactly mimics the OEM curve, only slightly worse.
Aside from saving 2.1 pounds, the AkropoviÄ slip-on has a slightly negative effect on the horsepower. In side-by-side dyno runs, the peak power dropped 0.8 hp, and the effect in the midrange was similar. Although a disappointment, this should really come as no surprise since OEM exhaust systems have gotten so good in recent years. The other thing to note is that KTM PowerParts makes no claim for increased horsepower. Rather, they are counting on our assumption that it will make more. Finally, I defy the typical rider to tell the difference that a single horsepower makes in a bikeâs rideability.
Yes, there is power to be unlocked by extracting the dB killer baffle in the slip-on (there are YouTube videos demonstrating how), but as I said before, I donât believe in overly loud pipes on the street. Personally, the sound is so pleasurable that I donât begrudge the minimal power loss â too much. (Donât worry, Iâm already working on finding more streetable power from future updates.) Letâs not forget that the weight savings is 29% versus stock, which helps to offset the power loss a little.Â
Finally, some people have told me they think the muffler is too big, but I think it looks pretty sweet. Beauty is, as they say, in the eye of the beholder. If you want a smaller EPA-legal slip-on, Yoshimura has one.
Although we had no problems with the stock Maxxis tires on the street, we opted for Dunlop Q4s for our track day during the shootout with the Triumph Street Triple R and rode with them on the street until we were well into the wear bars. Troyâs impression of the Q4 rubber on the track is that they get up to temperature quickly and donât require tire warmers. Unfortunately, he feels they sign off early when it comes to rear grip. However, this gave him the opportunity to feel how well the 790 manages its traction control. Where on some bikes the TC can be felt actively cutting power, the 790âs TC can be felt trying to feed out as much power as possible without slipping â an important distinction. On the street, the Q4s worked like the top-shelf sport tires that they are. However, we failed you because we neglected to write down the mileage when we changed to the Dunlops. So, we canât say how long they lasted. In our defense, we never really planned on keeping the 790 this long. It just sort of happened.Â
The Dukeâs current tires are the Michelin Power RS, a street tire that weâd only sampled on the track and that weâd been itching to try out on the street. Weâll give an update on them after weâve logged more miles, but our impression is that they are every bit as fun on the street as they are on the track. As with my first impression of the tires, they do slow the steering a little compared to the Q4s but not in a problematic way. So far, theyâve got a few hundred street miles plus one track day, and they appear ready to go significantly longer.Â
One common complaint about the 790 Duke has focused on the lack of initial bite from the front brakes. While I have not personally been overly bothered by this, I thought Iâd see if swapping out the stock brake pads for some EBC Double-H pads made a difference. In the past, Iâve had good luck with them. So, I thought Iâd see if they worked their magic with the KTM calipers and rotors.Â
After bedding the EBC pads in, I found that the initial brake application delivered much more bite, with their stopping power building linearly from there and giving a very precise feel at the lever. At the track, the EBC pads hauled the 790 down from speed with much less lever effort and greater feel â regardless of whether the bike was straight up and down or trail braking to the apex. Overall, I think that $40 for each pair of front pads is money well spent if youâre among the people who felt shortchanged by the stock KTM/J.Juan pads. Although I installed the $37 rear pads, too, I didnât notice much of a difference in braking power, which is probably due to the way I use the rear brake. I never felt anything lacking from the OEM rear pads.
One area that I usually focus on when modifying a motorcycle is crash protection. If I am unfortunate enough to have a mishap, I hope to be able to ride the bike home. My first steps towards this goal are the KTM case protectors. The Clutch Cover Protection ($75) and the Ignition Cover Protection ($75) are simple bolt-on parts that should help keep the oil inside your cases in a slide. The orange of the CNC-machined aluminum protectors looks great. Installation only took 10 minutes. Simply replace the 5 bolts that hold this armor in place (along with releasing and re-torquing the other cover bolts). Still, Iâm puzzled as to why the vulnerable water pump cover did not receive a factory protective option, too. Iâll keep looking for the appropriate piece in the aftermarket.Â
Finally, after being pelted with road debris that the sticky Dunlop Q4s were tossing at me as I followed Ryan on a Sunday morning canyon descent, I decided the Dukeâs radiator looked awfully naked. So, I ordered up an Evotech-Performance Radiator Guard ($130). This black powder coated, machined aluminum cover looks like it should have been part of the Dukeâs factory design. The front grill has a mesh that is fine enough to prevent damage from stones while still allowing ample cooling airflow. The guard is held in place by two side covers that wrap around the ends of the radiator and dress up what was a rather mundane part of the engine. The Evotechâs fit and finish make it look like original equipment and not an add-on part.Â
Moving the handlebar clamps to the forward hole on the triple clamp and rotating the bar forward opened the riding position up just enough to improve highway comfort and allow for a tuck on the track.
The 790 Dukeâs handlebar offers a good bit of adjustment. First, I removed the bar itself to shift the clamp to the more forward of the two mounting holes in the triple clamp. Next, I rotated the bar to the limits of the adjustment markings. This gives my upper body a little more forward lean into the wind on the highway without compromising the comfortable, mostly upright torso position that I like so much about the bike. Additionally, during track days, the new location of the grips provide a more aggressive body angle for attacking the corners â though I still need to slide my butt all the way back to the pillion coverâs pad to get my upper body out of the wind blast on the straights.Â
Thatâs it for Phase One of our KTM 790 Duke project. Iâve already got other plans for the bike, but for now, it needs to stay as functionally close to stock as possible. Why? Well, weâve got another shootout scheduled for it in mid-July.Â
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