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MD Project Bike: Dirck Modifies a 2019 KTM 790 Adventure, Part 2

19″ and 17″ wheels from KTM 1290 Super Adventure S installed on our 790 Adventure

If you read Part 1, you know that we are modifying a 2019 KTM 790 Adventure – the standard model, not the R (with longer, adjustable suspension and knobby tires). We started out by swapping the front wheel from the stock 21″ to a 19″ from a KTM 1290 Super Adventure S, which was a simple process as it shares all the relevant parts, including the brake discs.

Now, courtesy of KTM NA we have the 17″ rear wheel from the Super Adventure installed. Another straight swap that re-uses the stock brake disc and chain sprocket. We mounted another Continental Road Attack 3 tire (matching the front make and model tire) in a size 170/60 x 17.

The front tire swap resulted in a big speedometer error – a steady 80 mph (GPS verified) showed 89.5 mph on the speedometer after installing the smaller diameter front tire. To fix this, we contacted Ian Chappel (ian.n.chappel@gmail.com), located in Great Britain. Ian is known on a popular adventure bike forum for his wizardry at creating custom KTM parts, including ABS/tone rings.

Custom ABS/tone rings from Ian Chappel

To correct the roughly 12% speedometer error, Ian cut a 43 slot front ABS ring (the stock is 48 slot). With the smaller diameter rear tire, we simultaneously swapped in a 45 slot ABS ring there, as well. Ian’s rings bolted right on in place of the stock units, and the speedometer is now dead perfect (90 mph on GPS is now exactly 90 mph on speedo).

The front fork is greatly improved – largely due to a higher spring rate – shorter spring with much less preload. The initial harshness of the front fork is completely gone, although we are still playing with the fork valving (more about that in a future article).

New ABS tone/ring installed on front fork

Already, our modified 790 Adventure works much better on the street, particularly for cornering and braking where the much larger contact patches and the road tire profiles have made a huge difference. We were able to balance the weight distribution of the bike to our liking by playing with rear shock spring preload settings and sliding the front forks down a few millimeters in the triple clamps.

This bike now rails corners on the street and changes direction with much less effort. It is not just the larger contact patches from the new tires, but the reduction in inertia created by the removal of the 21/18″ stock wheels, and the new road profile of the tires. All of these seem to have contributed to a dramatic improvement in the handling of the 790 Adventure on the road. Stay tuned for more reports and more modifications to this bike.

23 Comments

  1. Mick says:

    I have often wondered why nobody makes a bike with a DTX setup (19 inch front and rear). DTX bikes can rail pavement, even with dirt track tires. They would totally be the way to go for dirt roads, and they would preform as well as anything without dedicated dirt rubber on softer surfaces.

    Maybe I should get a set of 19s for my supermoto and illustrate.

    Whatever, even bikes marketed as “scramblers” don’t have 19 inch wheels. I don’t get it.

    • Mick says:

      It came to my attention a short while ago that CCM makes what are basically DTX bikes.

      https://www.ccm-motorcycles.com/

      They are not cheap and they don’t have shaft drive, a center stand or a 17 gallon gas tank. But that is 1000% fine by me. If I was in the market for a new street bike the Foggy S Edition Spitfire would be on its way to my place.

  2. Donk says:

    I look really hard at the 790 Adventure but decided it was too off road biased for the riding I do. These 2 articles have me so excited I can’t decide if I should break the bank to do one myself or wait and see if KTM comes out with an 890 Adventure. Great job Dirck THANKS

  3. Brad Pope says:

    I did the same wheel swap on my KTM 690 Enduro. So now I have the option of a scrambler type thumper with the 17/19 combo of a true dualsport with the 18/21 setup.

  4. RyYYZ says:

    Why doesn’t KTM make this bike?

    Seems like they’ve got a fine light sport-touring package here and the makings of a generally good all-around street bike.

    I know, everybody thinks, or at least wants to look like, they’re going to do the Darien Gap.

    Still think bikes this size, regardless of how good they are, are still too big for me to be comfortable riding them in anything I would call off-road. Gravel and dirt roads, some light trails? Sure.

  5. Mick says:

    Neat trick with the tone rings. Too bad the speedo gets speed from the ABS system. Kudos to Ian Chappel for dealing with it.

    Odd that KTM doesn’t mix and match features on the KTM and Husqvarna street bikes like they do on the dirt bikes. It is nice that the wheels and stuff swap around pretty easily.

    I was surprised to find that my extra set of KTM wheels still work on my friend’s 2017 250XC-W but the rear doesn’t work with the larger axle on my 2017 300 XC. Darn!

    • guu says:

      I’m not 100% sure, but I think that rear wheel should fit with the right spacers. Bearing size, spacing etc. have remained the same for years.

      • Mick says:

        It can supposedly be converted. But then my buddies wouldn’t be able to use it.

        Maybe someone makes a quick swap conversion. Maybe I’ll have a look.

        I have extra sets of wheels to serve as a quick way to get me or my buds back on the trail. Hopefully I/we never need them. But you never know who is going to need them. Wheels take up a lot of space. So you don’t like to have to haul around too many.

  6. skortch says:

    Interesting and cool. My modifications to motorcycles usually involve making sport bikes into more comfortable sport tourers and my DR into a better offroad/adventure bike. After reading this and the previous articles I think I get the rational behind this experiment.

    Are you going to keep the original wheels with some knobbier tires, for those times you want to do some more dirt-biased extended rides? If so is it easy to switch between the two wheel sets? (Seems like it, if I’m reading correctly.)

    • Dirck Edge says:

      Will keep both wheel sets, although sharing brake disks slows down a swap quite a bit.

  7. Skybullet says:

    Sounds like Dirck is going to end up with a Super Standard. A street bike that will do it all well and be comfortable to boot.

    • Dirck Edge says:

      That’s basically the goal, although I would add that a fair amount of dirt capability will remain.

  8. Anonymous says:

    That bike must be a real canyon carver now Dirk. You will probably shock a lot of sport bike riders in the twisties. With the upright riding position and wide bars it will almost be supermoto-esque. Like the seed from the marriage of the KTM Adventure series and the Duke series. The scalpel with a low slung tank and a 19in front wheel. Who wouldn’t love that?

    • Dirck Edge says:

      Haha, yeah. The sport bike guys at the canyon hang-out just s##* their pants because the “supermoto from hell” rolled up. Seriously, though, this bike is so light to begin with, the potential is impressive with a few mods. The motor in the 890 Duke takes things to another level. Can’t wait to sample that in a Husky adventure bike next year.

  9. Walter says:

    I suspect that for anything but single track the 19/17 will work fine off-pavement with appropriate tires (lots of good choices). I did a 19/17 conversion on a 990 Adventure and it worked very well- used that setup almost all the time- only switching to the 21/18 setup when doing an off road event.

    I changed to an 1190 (standard) when they came out; and expect that I’ll get a 790 (or 890 if that’s the next one) if KTM offers a 19/17 with all the good stuff. Otherwise, I’ll keep the 1190 (over 47,000 miles at this time- solid as a rock).

    I really don’t understand why they didn’t do that when they brought out the 790- since the 1190 and 1290 models were essentially the same with the exception of the wheelsets and electronic vs manual suspension. Really puzzling.

  10. Dale Eckhardt says:

    And this is why I picked the standard Triumph Tiger 800 instead of the XC. But I also picked up a 500cc dual sport. Last year I added a 3rd bike, a Speed Twin. Now, all I am wanting is a 125cc run about street bike,,,,,,,, and a bigger garage space!!

  11. Dirty Bob says:

    KTM designs and (carefully) engineers a 790 Adventure. Why would anyone make changes to a perfect offroad bike.

    • Gary in NJ says:

      Probably because Dirck didn’t have a need for a perfect off-road bike, but rather a perfect (for his needs) on-road bike. That’s the funny thing about motorcycles; some only see the bike for what it is, while others see it for what it can be. I have 4 bikes in my garage right now…not one stock and two are unrecognizable from where they began.

    • Dave says:

      He explains his reasoning in the first article.

    • Tom R says:

      Motorcyclists that don’t tinker any factory’s “perfectly designed” bike are few and far between.

  12. Mark says:

    Will you be reporting on the effect these changes have on the offroad handling and performance of the bike?