Big Motorbike Maintenance

Project KTM 990 Adventure: Rescuing & Reviving An Iconic ADV Bike

“The most dangerous motorcycle ever built.”

This is a paraphrase, or maybe the exact title, from a magazine review I remember reading shortly after the KTM 950 Adventure S was first introduced in 2003. Obviously, I was intrigued. The author was waxing ironic by indicating that the engineering in this oddity of adventure motorcycles was of a level that allowed the rider to do things most likely beyond their abilities. Rolling along at what you think is a comfortable pace on a relatively smooth, curvy dirt road, and looking down at the speedo to see you are doing 130 mph is eye opening. It’s something that makes you realize the potential consequences of unleashing the full fury of what is arguably the largest consumer-friendly version of a rally bike ever built. That said, A bit of history is in order.

2003 KTM 950 Adventure Rallye
The original race bike that started it all, the KTM 950 Rally, had a lot in common with the production model. Photo: KTM

When KTM’s V-Twin LC8 platform was first released to the world in 2003 in the form of the 950 Adventure S, it was a game-changer. Based heavily on the KTM 950 Rally prototype, the bike wasn’t deemed ready for production until pilot Fabrizio Meoni had already won both the Pharaons Rally (2001) and the Dakar Rally (2002) aboard the machine. 

For several decades, manufacturers such as Honda, Yamaha, Cagiva, and KTM all started building twin-cylinder off-road monsters, and buck-and-a-quarter speeds at the Dakar suddenly became an almost common thing. The KTM 950 Rally was the last of this breed of large-displacement twins to race Dakar before being banned due to safety concerns about the speeds these dreadnaughts were capable of. What was unleashed to the public in 2003 was essentially a legalized rally bike capable of never before seen performance off-road for this class of motorcycle, even in its tamed production form.

With a chassis virtually unchanged over the next 10 years, the 950 Adventure S increased displacement to become the 990 Adventure R in 2006, and would continue on with only minor updates until 2012. As such a unique motorcycle design, the KTM 950/990 Adventure platform built a legendary reputation as an off-road capable adventure bike that still stands years after its discontinuation. 

2012 KTM 990 Adventure
The 950 Adventure S increased displacement to become the 990 Adventure R in 2006, and would continue on with only minor updates until 2012.

A Worthy Revival

Recently, a friend of mine reached out to ask me if I’d be interested in adopting his 2008 KTM 990 Adventure that had been sitting around collecting dust. Normally, this would seem like incredible good fortune, but having been on several trips with this bike I was well aware that it had not lived a kind or gentle life. This particular 990 checked the “hard travel” box more times than anyone can count. Where many big twins spend a decent amount of time at local coffee shops, this one had been lost at the bottom of a river in Mexico.

Near the highest point along one of Northern Baja’s trails, a large and normally dry floodplain began absorbing water from a storm a few miles away. In minutes, the route went from dry trail, to muddy mess, to a wall of water leading the way for a torrent to follow. While the water remained a manageable depth, the rider began crossing the plain. Before reaching the other side, a four-foot high wall of water came careening in from the distance, slammed the bike and rider to the ground, and carried both about 100 yards downstream until being stopped on a tree stump.

The 990 found and rescued after being swept away by raging waters in Mexico.

Fortunately, the rider was able to get out from underneath both the bike itself, and the crushing onslaught of water, and climb to safety. The 990 however, remained buried under the silty maelstrom for a half an hour until the flash flood waters finally began to subside. Only once the floodplain calmed from a raging torrent to a fast-flowing river was the bike able to be recovered with the help of a local rancher’s truck.

Countless trips in and out of various repair shops healed some of the wounds on this bike, but mystery problems persisted hidden somewhere deep inside the thing. When I received the bike, it started and ran but its erratic throttle response made it essentially unrideable. Chipping paint and scars from an abusive life were clearly noticeable. Yet with its Scotts steering damper, upgraded skid plate, luggage racks, and the monstrous exhaust note from its Leo Vince pipes, the overall platform was set up quite nicely.

KTM 990 Adventure bike build
The V-twin growl from its Leo Vince pipes is a thing of beauty.
KTM 990 Adventure bike build

Having owned a 2005.5 950 Adventure S which was probably my all-time favorite bike to ride, clearly I had an affinity for these machines. Unfortunately, that 950S was totaled in an incident on the street many years ago. This ‘basket case’ of a 990 had been written off as a lost cause by most, but for me I felt like it deserved to be back on the trail and I was willing to put in the time to attempt to fix it.

The Specs

Before diving into this moto-resurrection saga, what is this bike? By the details, the 2008 KTM 990 Adventure (standard model) is a 999cc V-twin inhaling through a very high intake and exhaling through equally high twin pipes. Producing a claimed 98 horsepower and 70.1 ft-lbs of torque at 6,500 rpm, this powerplant is connected to a 6-speed manual transmission and rides in a trellis-style chassis where it also serves as a stressed member.

KTM 990 Adventure project build

In stock form, this chassis has a wheelbase of 61.8 inches, 10.3 inches of ground clearance, and a seat height of 33.9 inches. Overall claimed dry weight for the bike is 438.7 pounds, and that weight increases by roughly 35 lbs as 5.8 gallons of fuel are added between dual tanks hanging from each side of the bike. All this rolls on a 21”/18” set of spoked wheels featuring Brembo brake calipers gripping twin 11.8 inch rotors up front and a single 9.5 inch rotor in the rear. WP suspension provides 8.3 inches of travel all around.

Getting The Engine Sorted

While the bike did start, and produced forward motion, it was roughly the equivalent of riding a mechanical bull powered by nitrous and the bad dreams of a thousand angry hippos. In short, a barely controllable powerband. Clearly there was going to be a lot of work involved, so first things first, take care of the more basic maintenance items such as oil change, oil and air filter maintenance, cleaning/lubing the chain, fuel filters, as well as draining and replacing the existing fuel of unknown age sloshing around in the tanks.

Convenience was clearly not in mind when considering the oil change procedure on the 950/990. The factory service manual goes so far as to state, “Since many parts must be demounted for an oil change, we recommend having the engine oil changed by an authorized KTM workshop.” In addition to most of the front end body work needing to be removed, the left-side fuel tank also has to be removed for this process. 

KTM 990 Adventure bike project build
We gave our project bike some fresh quarts of Motul 7100, an ester-based full synthetic designed for high-performance bikes like the KTM 990 Adventure.

 The unique dual-tank design of the 950/990 is a double-edged sword, depending on whether one is looking at the bike from a riding perspective or a maintenance perspective. This design allows the bike to be amazingly slim like no other bike in this class at the time, while keeping the fuel weight lower. When it comes to maintenance, this means a lot of bolt spinning as the bodywork and fuel tanks need to come off for almost any procedure related to the motor.

Fuel filters can tend to be neglected on the 990 because they are tucked away inside the fuel pump, which is tucked away inside the fuel tank. Once removed, the fuel pump itself needs to be disassembled and reassembled to gain access to the filter. While not an overly complex procedure, there are certainly many steps involved.

KTM 990 Adventure bike build
Changing the fuel filter requires removing the left-side tank and the fuel pump, then disassembling it to access the filter inside the pump itself. While not rocket surgery, there are several steps involved, and replacing all seals is highly recommended.

With the right-side tank removed and the air box opened up, ports on the throttle bodies can be accessed to allow them to be synchronized or “balanced.” The idea is to ensure each cylinder is receiving the same amount of air through the butterfly valves, and the difference in a motor with properly synced throttle bodies versus an out-of-sync setup is staggering, especially at or near idle. 

Further steps taken to try and tame this beast included less basic maintenance procedures including replacing an extremely dirty fuel filter, balancing the throttle bodies, replacing and adjusting the throttle position sensor unit, and performing what is known as the “15 minute” ECU learning fix – a process that allows the bike’s ECU to relearn optimal settings for the bike’s current environment.

KTM 990 Adventure bike build
The old battery was shot so we put in a Fire Power Lithium Battery that puts out 310 cold cranking amps and weighs just 2.4 pounds compared to 230 CCA and 8.6 pounds for the replacement AGM battery.

Once some of these more perfunctory mechanical duties were taken care of, the larger issues began to reveal themselves. A massive “detent” in the throttle response right off idle which morphed into a bucking bronco effect toward the mid-range. With the use of TuneECU software, 18 different fuel maps were tested in an attempt to correct this problem, but to no avail. Each map altered the characteristic of the engine and would change the symptom, but never fully correct it.

KTM 990 Adventure bike build
As many as 18 different fuel maps were tested in an attempt to correct our fueling problem.

Feeling a bit stifled with our progress on the project, we asked the master mechanics at KTM North America HQ to check if the ECU was defective. What they found was a myriad of other things instead, caused by age, neglect and various failed troubleshooting efforts over the years, that contributed to the erratic fueling symptoms we were experiencing. Mis-adjusted throttle cables, incorrect ignition curve, and loose wiring were among the gremlins lurking in this machine.

After having many of these things corrected, the bike was now rideable but still had a brutal stumble at around 4000 to 5000 rpm. Our friends at KTM suggested a couple of things to check into that were likely the cause of the final fueling issue. The 990 has three MAP (Manifold Air Pressure) sensors — one on each throttle body and a third in the front cowling behind the instrument cluster. Given time and the right conditions (such as being drowned in a silty river in Mexico), these sensors can become dirty and clogged, potentially causing a stumble at certain RPM ranges. 

KTM 990 Adventure bike build
Replacing cracked vacuum lines and cleaning the MAP sensors would reveal an entirely new motorcycle.

Upon inspection, it was immediately apparent that the short vacuum lines connecting these sensors were cracked and leaking. Replacing these hoses and attachment points, cleaning all three MAP sensors with a de-oxidizing electronic parts cleaner revealed an entirely new motorcycle. Possibly the smoothest and best-sounding 990 Adventure I’ve ever ridden. 

Refreshing The Chassis

Among the list of maintenance performed, even those more straightforward sounding bits took on unusual forms in this project. For example, changing fork oil. While that is arguably a level 1 or 2 task, what made it unusual is that we were not changing the oil in ‘this’ bike’s forks. 

KTM 990 Adventure bike build
2005 KTM 950 Adventure S donor bike before it was totaled in a crash.

As mentioned earlier  in this story, I also own a 2005 KTM 950 Adventure S which was totaled in a crash. While riding this bike some years ago I was unfortunately hit by a VW Jetta when it decided to suddenly zig instead of zag mid-way through an intersection in LA, resulting in quite a bit of damage including a broken frame. Thankfully, I was able to purchase it as salvage and it came in handy as an organ donor for this project bike. 

In stock form, the 2005 950 Adventure S featured a fork spring rate of 0.48 which I had previously upgraded to stiffer 0.52 springs and re-valved the suspension. In turn, the rear shock remained mostly stock, aside from a spacer which was removed to increase the travel to its full potential. These changes increased the overall height of the bike so much that the center stand and side stand had to be lengthened. 

KTM 990 Adventure rescue build
The fork oil hadn’t been serviced in over a decade. What came out was a nasty chocolate milk color with barely any viscosity.

The forks of our 2008 990 Adventure project bike were significantly shorter than the older 950 Adventure S’, and were also in need of some dire maintenance. Rather than put the effort into the 990’s shorter legs, we opted to swap both the forks and rear shock from the 950 S to bring our project bike a bit closer to its original rally heritage. With the suspension swapped, the wheel travel, seat height and ground clearance were now raised 2 inches higher than stock.

KTM 990 Adventure bike build
The suspension swap also required a long ‘S-model’ center stand and kickstand.

This swap led to some interesting challenges, as the older 950 did not possess ABS, and thus the mounting points on the fork stubs for things such as wheel sensors and fenders don’t quite line up. There were enough available threaded options to allow everything to be assembled, and only on close inspection can the differences between the model years be seen. Another key difference between the two models is the side stand killswitch, which didn’t exist on the 950 Adventure. A 2012 OEM 990R side stand was sourced as it incorporates a magnetic kill switch tab and has the required length to handle the taller suspension.

KTM 990 Adventure bike build
We replaced the old fork oil with Motul Synthetic 5W to give the front end that ‘fresh from the factory’ feel.

While the brakes were working, fluids of unknown age and condition were replaced to enhance stopping performance. The typical method of bleeding air from the systems by pumping the master cylinders until all air is purged is effective, but can be time consuming. A vacuum pump brake bleeder was used to more efficiently pump out the air and replenish the old brake fluid with fresh Motul DOT 5.1.

KTM 990 Adventure bike build

Saving one of the more obvious and immediate upgrades to the bike for last — the tires. A set of the old-style Heidenau K60 Scout hoops of unknown age was mounted on the 990 when we received it. They had clearly been on the motorcycle for a long while, and the rear tire was squared off to the degree it resembled a car tire more than a motorcycle tire. These were swapped out for a fresh set of Dunlop D606 front and D908 Rally Raid rear knobbies, which further enhance the KTM’s rally-like performance.

KTM 990 Adventure bike build
KTM 990 Adventure bike build
We swapped the old tires for a fresh set of Dunlop D606 front and D908 Rally Raid rear knobbies to get the bike ready for Baja.


One thing that definitely set KTM’s first twin-cylinder motorcycle apart from the pack when it was first introduced in 2003 is aesthetics. This bike simply looked like nothing else out there, for better or worse. Even the various color schemes and rally-esque models like the 2004 “GO!!!!!!!” bike stood out from the pack. Over time, the paint used in these vivid color schemes proved to struggle with remaining attached to the fuel tanks, and would eventually bubble and flake off on most bikes which had seen higher mileage and more extensive off-road use.

KTM 990 Adventure ADV Pulse project build
The saddle was refreshed with a new cover from Seat Concepts but the paint is in bad condition and still needs to be addressed.

Our test 990 was no different in this regard, and was suffering from this dreaded motorcycle dandruff. For some reason, the right side looked like it had been through a war, while the left side, only a few skirmishes. The seat as well, was severely faded with a couple small holes, so it received a new cover from Seat Concepts. New graphics are another visual upgrade we’re considering to further bring this legendary machine back to its former glory. 

The Final Stretch

Aside from a few tweaks on our to do list, the bike is now prepped and ready for a real adventure. Plenty of these levithan dirt bikes are still going strong, and a Baja run with a few other 990s is in the planning stages. Given this particular bike’s challenged history, throwing it into the gauntlet of Baja’s remote and rugged terrain is both a fitting test and an opportunity for redemption after its last trip down south. 

KTM 990 Adventure bike build
KTM 990 Adventure bike build
Stoked to have our 990 back on the trail and we can’t wait to let those twin pipes roar out in the open desert.

I’ve been riding almost exclusively modern machines these past few years, many of which have been much lighter, bleeding-edge tech middleweight adventure bikes. Climbing back aboard KTM’s first twin-cylinder motorcycle design may sound like something that would be a toned-down walk through the land of vintage motorcycles. But after thumbing the starter and hearing the percussive bark that roars from this machine you’re reminded that this is a bike that was banned from the most difficult rally in the world because it was simply too fast and powerful. Stay tuned for part 2!

Photography by Rob Dabney and Jon Beck

Author: Jon Beck

Jon Beck is fulfilling a dream of never figuring out what to be when he grows up. Racing mountain bikes, competitive surfing, and touring as a musician are somehow part of what led Jon to travel through over 40 countries so far as an adventure motorcycle photographer, journalist, and guide. From precision riding for cameras in Hollywood, to refilling a fountain pen for travel stories, Jon brings a rare blend of experience to the table. While he seems happiest when lost in a desert someplace, deadlines are met most of the time.

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