KTM 950/990(LC8) Emissions Reference

By: cpmodem

There're lots of variations of the Canisterectomy, mainly because there are a lot of variations of the Canister. The parts used and the method the factory used varies from year to year, and even from country to country in a single year. This was KTM trying to meet the requirements of an eclectic bundle of emissions standards worldwide. The following is a description of the canister packages found on the 950/990 over the various years.

Don't do like many folks do and confuse the Evaporative Canister with the Supplemental Air System (SLS). They are two seperate, non-interconnected emissions systems. The SLS (AKA SAS) is a passive system that allows fresh air into the exhaust manifold downstream of but near the exhaust valve. It raises the oxygen percentage of the exhaust gas and aids the Catalytic Converter (CAT) in reducing NOX ( nitric oxide (NO) and nitrogen dioxide (NO2) ) emissions to the atmosphere. Removing or disabling it has little immediate effect one way or the other on engine running or performance. Albeit, it does reduce one source of vacuum leaks over time. It does, however, reduce the CAT's effectiveness at reducing NOX, and over time will cause them to fail prematurely. It is ill advised to remove/disable the SLS without removing the CATs or installing aftermarket non-CAT exhaust cans, as the gains are minimal. Especially on the FI equiped bikes.

The Evaporative Canister Filters hydrocarbons from the fuel vapors in the fuel tanks and (on carbureted engines) the float bowls with activated charcoal before venting to the atmosphere. The vent lines from the tanks and/or bowls can become pinched or clogged with liquid fuel during the "normal operation" of a dual sport bike like the KTM. The results of which can range from the inconvenience of a poor running engine that stalls and runs rough, or doesn't feed fuel equally from both tanks, to a engine that becomes hydrolocked with raw fuel, to an explosive ejection of fuel from the fuel tank fill that douses the rider with flammable liquid. Removing the canister and properly venting the fuel tanks and float bowls has no adverse effects on the engines running or durability. It does do wonders for the reliability and driveability of the bike though.

For the record, in the USA, the canister plumbing and function was as follows (you won't find any description of the Evaporative System's operation in the Manuals):

Early 2004 (silver wheels, black un-painted ft fender):

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Evap Canister
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Late 2004 (black wheels, painted ft fender) through end of 2006:


canister 07
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The 990's (Adventure, Super Duke, and Supermoto):

*** 2010 and Later Adventure 990 and 990R:*** As of early 2011 we haven't had any reports of issues with the canister on these bikes. Some have even proclaimed the issue mute. So, until we get more data, I will advise owners of these newer models to ride them as delivered from the factory until issues of uneven tank feeding, gasoline geysers, and poor running associated with flooded canisters or pinched fuel tank vent lines show themselves. If you are the owner of a 2010 or later 990 Adventure please report any issues that come up pertaining to the fuel tanks or canister either to the Webmaster or at Advrider.com on the Orange Crush forum.


There is a Tech Bulletin (TB 0741) that mandates the installation of a "balance" tube between the two tanks at the top. This is KTM's way of mitigating the pressure imbalance between the tanks caused by a flooded canister system, without removing the canister (which they can't). It does balance the pressure between the tanks but does nothing to address the over/under pressure problems caused by pinched/clogged tank vents or clogged cap vent passages. Unfortunately, it wasn't thought out or executed very well, and the parts supplied in the "upgrade" kit are suseptable to failure when exposed to gasoline. Dad2dad wrote an article that describes how he removed the bypass and plugged the holes in his tanks.

Image by FastEddy760

Proper tank venting will go a long way toward keeping over pressure situations from occurring. However, the tank vents are still at the mercy of the caps, as all vapor in or out of the tanks must pass through the labyrinth in the caps as long as the flaps are intact. This works OK until liquid fuel gets into the cap passages. Such a scenario is prevalent in hotter climes when full tanks are exposed to hot engine, exhaust, and ambient air. Once the caps' tiny little passages are blocked by liquid fuel, no amount of good ventilation on the other end will help avoid "explosive over pressurization". A few of us found this out the hard way several hot summers ago. That is when the Flapendectomy was born .... out of necessity.

Most, if not all, of the canisters have caused problems for their owners. This manifests itself in the failure of the tanks to balance fuel levels between themselves. The resulting signs and symptoms are:

Remember, the bike ran fine as originally designed by the engineers in Mattighofen. Once we get this "add-on" carp feces off the big Katoom, it will run, once again, as designed.

Removing the canister (Canisterectomy) is a rather simple process, and becomes obvious once the parts are visible (remove the airbox and carbs).

This photo is of the Mikuni vacuum valve that is bolted to the outside bottom of the airbox on all USA July 2004 later 950's. The inlet of the valve is connected to the carb bowl vents inside the airbox (via a "Y" that was added in late '04).The outlet is connected to the canister (located in the left front fairing) via a "T". The other side of the "T" has a short length of hose with a knurled plug in the end. This plug is removed to drain any liquid gasoline that drains from the carb float bowls after a tipover. A single vacuum line runs from the front left intake manifold to the valve to actuate it with manifold vacuum when the engine is running. The barbed fitting in the intake manifold should be removed and a screw inserted to plug the hole.
(photo by NothingClever)

In the image below, looking through the right side triangular cover on the airbox, you can see the two carb bowl vent lines where they join at the "Y". The vacuum valve is directly below the "Y". You can see the two bolts partially loosened protruding into the airbox. The othes hoses (with spring coils over part of them) are the fuel lines from the fuel pump (in the skid pan area) to the two carbs. This hose is disconnected (at the joint midway down the leftside of the engine) in order to remove the carbs. (photo by NothingClever)

The photo below shows the intake manifolds with the carbs removed. These are the 4 vacuum ports that have to be tended to when the canister is removed. Run the two vacuum hoses from the right side of the intake manifolds to a point on the frame near the rear of the airbox and secure with a spot-tye, so that they can be reached by simply removing the seat. Thus the sync can be checked, and if not out of spec, no further disassembly need be done. Be sure to plug the hoses securely (I use screws of the appropriate size).
(photo by bmwgsbill)

From July 2005 on, there is another vacuum valve located next to the canister (shown in the next photo) in the front left fairing with a vacuum line running to the rear intake manifold. Remove the barb fitting and plug that hole as you did with the front. Some folks take a shortcut here and either plug the vacuum hoses, or remove the hoses and cap the barbed fittings. They're just leaving a potential opening for leaks in the future. Take a few extra minutes and do the job right. Use two M6x1x10mm bolts to plug the vacuum ports on the left side of the intake manifolds, It's not easy to access this area if you have problems in the future. This is no place to do a "Mickey Mouse" patch job.

The 990 FI models have an ECU controlled electric "purge valve" for the canister. The valve can be left connected to the ECU wiring with the vacuum and vent lines removed and the holes plugged properly with screws at the intake manifolds. If you want to remove the purge valve completely, the two wires fron the ECU must be terminated with a resistor (15-22k ohm works fine), or the FI warning light will stay on. Again, here's FastEddy's article 990 Error Code Bypass

For a good step by step how-to of a typical Canisterectomy and SLSectomy see Groomez's excellent photo rich article elsewhere in the HOW.

Now, a couple of points:

1. The original production LC8 carbs were vented with two (2) separate lines directly out the bottom of the air box. The front carb was 275mm(10.8") long. The rear carb was 250mm(9.8") long. No filter, "Y", or any other device was attached to these vents. The carbs were tuned by the factory to work with this configuration. They can be tuned to work with just about any other configuration, but why bother. Simple is usually best.

2. Carbs (especially CV carbs) inside air boxes, like the KTM 950, are notorious for being sensitive to float bowl venting. The 950 exhibits poor venting as a part throttle miss. There's a good reference to this phenomenon by Factory Pro dyno tuner Marc Salvisbergover at their website fp logo

3. The original Desert racer LC8's vent each tank individually with hoses running straight down the sides of the radiator to just below the bottom of the tanks. The Dakar Rally bikes fitted small plastic fuel filters about midway. Which would be a good idea if your riding in a lot of dust. Top two photos are my 2004 950. The next photo down is Fabrizio Meoni's "Works" Dakar Rally bike. DO NOT ATTACH ONE-WAY VALVES TO THE TANK VENT LINES. These devices have caused the very same problems as the canister by pressurizing the tanks. This has been common knowledge for years now, yet folks continue to install them. Just don't do it. 'Nuff said.

Note: The fittings you see in the top front of each tank do not go directly into the tanks as many folks believe. They are plumbed internally to the fuel caps first, then into the tanks through the caps.

Dakar Tank Vent

4. The original desert racer LC8's did not have charcoal canisters, EPC valves or an SLS/SAS system. Nor did they have CATs, TPS's, clutch/neutral/sidestand safety switches, or rear cush drives.

5. There are one way flapper valves and a labyrinth of small passages built into the OEM fuel caps that work with the canister. For the tanks to vent properly under all conditions, these must be removed (after or during the Canisterectomy, of course). When done properly, the tanks will be able to "breathe" equally in both directions. See Flapendectomy for more info. *


So, it would be a good start toward getting any LC8 to run as it was originally engineered to run, by removing all of the add on carp feces and return it to as near as possible to the original design.

I know lots of folks have done it differently. KTM even issued a Tech Bulletin to add an upper cross connection between tanks (which does nothing to address the tank venting problems, it only equalizes the air pressure between both tanks). Lots have had success with their methods. Some have not. That's fine. I'm just describing an alternative to all of the various designs. A single, simple, back to the basics, get rid of the complexity, K.I.S.S. (Keep It Stupid Simple) solution that has worked for me.

*Also, please folks, don't try this at home. Leave dangerous procedures to the expert professionals. Also this modification is not approved by the EPA, EUC, or the NBA. So only use these "modified" vehicles for off highway, closed course, racing activities. YMMV. Yada, yada, yada...