How To Re-Jet the 950

This is an article documenting the installation of the Head2Wind jetting kit on my 2003 950. Its not a difficult task, even for a novice, and if H2W’s printed instructions are followed to the letter, most folks should be able to complete this procedure without problems. It’s a good idea to read through the entire procedure before taking wrench to bike. Also, it’s a very good idea to have the Repair and Parts Manuals for your particular bike to refer to as you proceed.

To get to the carbs for installation of this kit you need to remove almost as much stuff as when doing a valve check, so it makes sense to do both at the same time.

First remove the seat (unlock with the ignition key on the left side).

Then remove the glove box. At this stage you are at the point where you can service the air cleaner (after removing the air box cover), or check the carb sync.

Next, remove the fuel tanks.

Remove the air box cover (eight screws) with an 8mm socket. The screws will stay with the cover. Then remove the snorkel or pre filter (4 screws). Twist the air horns CW to release and remove the main air filter.

Remove the three screws and remove the triangular access cover on the right side of the air box with a 6mm socket (or nut driver). Removing the left side at this time will aid in hose removal later, so go ahead and remove that one while you’re at it.

Use an 8mm socket on a long extension to reach through the access and loosen the rear carb clamp (top one of the two). 1/4″ drive works best here.

Then loosen the front carb clamp. These clamps don’t need to be removed, but they do have to be loose enough to allow the shoulder of the carb to slide out. Then loosen the hose clamps on the fuel lines where they go into each carburetor and free the hoses. Be prepared for some fuel to leak from the carbs and hoses during this and later steps. Extinguish all open flames, etc.

Once the carbs are free of the boots, push the idle adjustment knob and its grommet up through the bottom of the air box Leave it attached to the carbs.

Also push/pull the carb bowl vent hoses up through the bottom of the air box The vents shown are the original ones from an’03/early ’04. A Tech Bulletin replaces these with thicker hoses. If you have a later model 950, it will have a single hose that comes from a “wye” the joins the two vent lines. See CANISTERECTOMY elsewhere in this HOW for more info on the various venting systems for your year bike.

If you’re unlucky enough to have Electronic Power Control (EPC), you will need to disconnect the two hoses that run from the EPC valves, through the air box, and connect to the black plastic diaphragm covers on each carb. This system reduces the acceleration of the engine in 1st and 2nd gears to aid in passing the European noise tests. It is found on all EU and AUS spec bikes and only on early ’04 USA models which are actually EU ’03’s. Again check out the link above for CANISTERECTOMY for more info on this system, if it applies to you.

At this point, the carbs are free enough to work on for the purposes of this kit, but I prefer to remove them from the bike completely and do the work on my work bench. So the enrichment cables (purple arrow), two throttle cables (green arrow), and Throttle Position Sensor (TPS) (yellow arrow) need to be disconnected.

Unscrew the enrichment cables from each of the carbs with a 10mm spanner.

Use the 10mm spanner to loosen the throttle cables from the carbs (green arrow). The ends of cables will be easier to disconnect from the bell crank (red arrow) if you adjust for maximum slack at the twist grip on the handlebar. Careful not to damage the cables. A pair of surgical hemostats work good in intricate operations such as this. If you have problems getting the cables loose from the bell crank, removing the other end from the twist grip will make it much easier. I didn’t need to do that in this case. Use your good judgment here; you don’t want to damage the throttle cables.

Finally, unplug the TPS connector (you will see it if you look on the left side of the bike between the radiator and the air box. If you pull the TPS off the carb, you will need to recalibrate it when you re-install it. No need to do that unless you’re tearing the carbs down completely.

If your bike has carb heaters (most do, mine doesn’t), disconnect the two connectors and snip the zip ties holding the wire loom to the carb braces. Be careful not to nick/cut the wires. (photo by PvtIdaho)

Voila! The carbs are now free to take over to your workbench. For illustration purposes I have pointed out some of the parts you will deal with: The carb bowl vent on the rear carb(red arrow), air horn adapter (blue arrow), diaphragm cover (green arrow), TPS (yellow arrow), and float bowl (magenta arrow).

Now remove the air horn adapters with a 4mm allen wrench. Also, take off the diaphragm cover with slide assembly and large spring from each carb. Note that I have marked each carb (RR/FT) for easy reference later when the jets are installed.

Flip the carbs over to access the float bowls. Remove the four phillips head screws (green arrow) from each float bowl cover, remove the covers, clean the insides with carb cleaner and set aside. Typically, they will be very tight, so use a proper size screw driver head. I use precision hollow ground gunsmith screw drivers for this job. The red arrows point out the *Idle Air Mixture Control Screws for reference in later operations.
*NOTE: Idle Air Mixture Control Screw is the description KTM provides in their Repair Manuals when describing our Keihin CVRD 43 carburetors. I use KTM’s nominclature in this article to provide continuity and to lessen confusion for readers of both references. KTM also refers to this same part as the “Idle Mixture Screw”, “IMS”, and just plain “Mixture Screw”. For the purpose of this article, we will assume that they all refer to the adjustment screw for the low speed circuit. A more “correct” description would be “Pilot Mixture Screw.” If you would like to read more about the inner workings of the Keihin CV carburetors there is an easy reading article on the Ninja Riders website.

The floats and fuel jets are now accessible:

You don’t need to separate the carbs for any of these procedures. Hold the carbs so that their floats press lightly on the needle valve as you take the measurements. Measure from the highest point on the float to the adjacent gasket surface. Be careful not to press against the float and don’t leave a space. It’s a gentle touch that’s required. Take your time and get a good measurement.

3mm is the spec. My front float:

My rear float:

I like to know exactly what the float level is, so I use a digital caliper. A depth mic will also work. Below is a photo of the KTM “go_no_go” tool (60029016000), if you just want to check/set the floats to 3mm. It’s $26 from KTM-parts.com.

To adjust the float level, carefully and gently bend the tang on the float to get the desired measurement. Several adjustment/measurement cycles will probably be needed to get it just right. The front measurement I got was about as close as I could get with the adjustment provided, so I left it alone. The rear was much too far out, so I tweaked it until it was as close to 3mm as I could get it.

FYI, the greater the number the leaner the effect on fuel mixture; the smaller the number the richer. This may come into play later for fine tuning the mixture for idle and low rpm’s, but 3mm worked fine for my application. There is some very detailed info on this and jetting in Ken’s instruction sheet that come with the kit. Very possibly worth the cost of the kit by themselves. If you don’t have the kit, Factory Pro has some very good info that is generic to CV carbs that will help if you want to get deep into tuning your CV’s. For the purposes of this kit no other tuning is necessary.

I removed the floats and needle valves to inspect and clean the parts. Especially the condition of the needle valve tip and its respective brass seat. These parts are critical for the carbs to maintain the proper float level and, also, keep fuel in the tanks from leaking past and filling the cylinders when the engine is off. Don’t mix the needle valve parts from one carb to the other as they may have worn in differently. Lots of little parts and springs to misplace here folks. I’d only remove the floats on the bench to avoid dropping the itty bitty bits into the engine recesses. Just sayin’.

Remove the *Idle Air Mixture Control Screws with the spring, washer, and o-ring. Refer to the image above for their location. Keep track of which one goes with what carb and don’t mix them up. Again use the proper hollow ground precision slot screwdriver on all of these jets and other brass parts. The #4 found in a good gunsmith kit is a perfect fit. The right tool for the right job, and all that.

The *Idle Air Mixture Control Screw and its related parts in their order of installation. Clean the screw and set aside.

Next remove the main jet (MJ). The one that the screwdriver tip is pointing to is the MJ.

Then remove the Low Speed Jet (LJ) as shown below.

Remove the Main Jet holder with a 6mm socket, nut driver, or jet tool. Clean the jets and holders with spray carb cleaner. Don’t stick anything hard in the jet holes (ie: drill bit, torch tip cleaner, etc). They are calibrated based on specific tapers and finish. If altered they will no longer flow the same. Be forewarned.

Next remove the needles from the slides by squeezing the plastic retainer with your fingers. Careful not to loose the small parts (small spring and two washers) when you remove the needles from the holders.

This is what the #3 position looks like. Note that the thick washer is on top and the thin on the bottom. If the clip is moved to the right, it lowers the needle and leans out the fuel air mixture. Visa-versa when moved to the left. Ken suggests #3 and that is where I left mine (previously moved them there from stock #2 years ago to help cover the lean midrange that the 950 comes tuned to from the factory). Re-install the needle into the holder, then the holder into the diaphragm. Set aside for installation into the carbs later.

These are the jets you will install from the kit. Be careful not to over tighten these little gems. They are soft and so are the aluminum carbs. Just “snug” is the right way. Also, use the proper size flat blade screwdriver tip. Its easy to mess up the smooth flow through a jet with a sloppy fitting screw driver. If you do that, you would have been better off to leave it stock. It should fit without any slack. As I said before, I use precision gunsmith screw drivers.

  • The main jet (MJ) is top right. Front is #148. Rear is #152. Stock is 155/160.
  • The #45 low speed jet (LJ) is on the Left. Stock is #42
  • The Idle Air Jet (IAJ) on the bottom right is #70. Stock is #50.

The IAJ is #3 in the below image from the Repair Manual.

 

Re-install the *Idle Air Mixture Control Screw’s back in their respective spots, taking care that the spring, washer, and o-ring are in the proper order as shown earlier. Lightly seat each CW and back them out 1.75 turns CCW.

Install the MJ holders, then the MJ’s (148 ft, 152 rr). Just snug them up. Don’t go ape sh** on them.

Next re-install the LJ’s (45). If you removed the floats/needle valves for cleaning. Re-install them now and re-check the height. Replace the bowl covers (make sure the gaskets aren’t damaged), check that the bowl drains are closed.

Flip the carbs over and remove the #50 IAJ’s and replace them with the #70’s from the kit as shown in the photo above. Re-install the air horn adapters.

Re-install the slides. Take care to:

  • Handle the diaphragms carefully and don’t get carb cleaner (or anything else) on them.
  • Guide the needles into the needle jets as you insert the slides into their proper locations in the carb bodies.
  • Carefully seat the diaphragms in their respective grooves in the carb bodies. Then, taking care that they are seated properly, set the spring on top of the diaphragm with the cover on top. Check that everything is seated properly by lifting the slide with your finger while holding pressure on the cover. The slide should move smoothly. It should return to the closed position when released with the damping action of the diaphragm apparent. Secure the cover with the screws just snug (don’t over-tighten).

Then reassemble everything in the reverse order of disassembly. Take care that the rubber vacuum lines are in good condition and that the rubber carb to manifold boots are not cracked or cut, and insure that they are seated properly so no leaks occur.

  • Insure the rubber grommets are in place in the bottom of the airbox, then insert the airbox over the intake manifolds.
  • There are rubber tabs molded into the carb to manifold boots that align the clamps so that they face the right way to be tightened/loosened through the access panels. Insure the clamps are engaging the tabs.
  • Install the carb to manifold boots on the intake manifolds and snug up the manifold clamps.
  • Many folks don’t loosen the carb side clamps enough. There is a lip on the carbs that has to fit past the clamps.
  • Seating the rear carb first then the front seems to be the smoothest.
  • Nothing should have to be forced. Some have sprayed a little silicone into the rubber boot to help the carbs slide in smoother, but if the clamps are loose enough the carbs will pop in with very little effort without lubrication.
  • Watch the boots as you press down on the carbs and make sure that an edge doesn’t get folded under. That is what tears them.
  • Don’t over tighten the clamps. Snug enough so that the clamps resist rotating when gently pushed is all that’s needed.
  • Check for smooth action of the throttle and enrichment lever. The throttle should snap closed when released with the handlebars in any position. If this isn’t right fix it now.
  • Also check that the fuel lines, carb vent lines, and fuel tank vent lines are not pinched.

Check the synchronization of the carburetors as outlined in the Carb Synchronization article elsewhere in the HOW.

In my opinion, the results are well worth the little bit of time and money invested. I thought my 950 was running just fine the way I had it, but with the installation of Ken’s jets, and the Uni-Filter pre filter, she now runs much cleaner and crisper. Throttle response is instantaneous and there is no lean surge or rich sogginess. A bonus is the easy to clean pre filter to keep the main paper filter clean for many 1000’s of miles. Even when used in extremely dusty conditions. I like being able to start each day with a clean pre filter. Preliminary fuel mileage figures are encouraging too. The first two tank full’s resulted in 39-40 mpg (a 3-4 mpg increase from my usual average). This is with riding lots of wheelies and 9000 rpm shifts (gotta make sure the jetting is right, don’t ya know). I’ll update this figure when I get another 10k miles on it.

Below is a dyno chart of Nightstalker’s 950 before and after the H2W kit was installed:

Nightstalker: So, the purple graph is my 950 this morning, before the installation of the prefilter and jet kit. The carbs at this point are stock with the exception of the needles being in the third position. Bike is de-smogged and has FMF slip ons. The torque dip at 3000 RPM was no surprise and matched seat of the pants experience.

The green graph is 4 hours later today, after completing the prefilter, jet kit, and carb cleaning. Apart from the included jets, no other modifications were made. Needles were retained in the third position. Maximum HP was reduced by 1 HP and max torque increased by 0.2 lb/ft. The increase and smoothing of the torque curve at 3000 RPM is very noticeable while riding.

Now get out and Go Ride!

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