Idle Air Mixture Screw Access

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Fundy Rider, Jul 13, 2013.

  1. Fundy Rider

    Fundy Rider Where 2?

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    Just took an eight hr trip to get the bike serviced. The idea was to get an lc8 tech. to do the valves, synch the carbs, set the tps and cure my somewhat rough idle that fluctuated maybe 50 to 100 rpm or so but ran great.

    It's an 05.5 950 adv. with 26000kms

    Everything in spec I was told. Left gassed up and after eighty miles or so I come to realize the idle is hung up around 2200 and then will fall to 1200.

    Not very happy! Talked to tech and was told he blocked a couple vent lines from the sas that was previously removed may be causing the idle issue with a rich condition. Makes sense.

    I am rambling so I will get to the chase. Do the carbs have to be removed to access the Idle Air mixture Srews?

    Or can a tool be made?

    Lesson learned keep wrenching yourself.
    #1
  2. Boatman

    Boatman Membership has it's privileges ;-)

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    #2
  3. mcmann

    mcmann Motorcycle ADV enthusiast

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    Sounds more like the pilot jets small side holes are partially plugged . . . Try a strong dose of SeaFoam (when the tanks are very low) . . . Let it sit over night after running for a few miles first.

    Ethanol fuels plug things up if the bike sits for very long.

    Normally, OEM 2.25 turns out is the best for the idle mixture

    http://www.ktm950.info/how/Orange Garage/carbs and FI/Jetting/jetting_index.html

    Idle mixture screw settings, float level and idle air jet size are the primary sources of mixture delivery during 4000 rpm steady state cruise operation.
    If lean surging is encountered, richen mixture screws (turn out) in 1/2 turn increments. Alternative idle air jets are can be installed if required.
    Idle mixture screw settings, float level and idle air jet size also affect high-rpm, 0 to 1/8 throttle maneuvers. Too lean, will cause surging problems when the engine is operated at high rpm at small throttle openings! Opening the mixture screws and/or increasing idle air jet size will usually cure the problem.
    #3
  4. gefr

    gefr Life is a trip

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    You can hear it geting smoother as you tinker with it.
    Cheers.
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  5. Fundy Rider

    Fundy Rider Where 2?

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    I have ran the bike plenty after the winter and has been running fine since coming out of storage.

    I also put star tron ethanol fuel treatment in the bike. A heavy few doses once out of storage for the winter and put some in every once in awhile during riding season.

    The only changes made were the blocking of two vent lines that were from the sas system that have been removed since the bike had 2000 miles on it.

    It makes total sense that the idle circuit would be rich now with those lines blocked.

    Unless I am missing something or don't understand. Why would anything be clogged in the pilot circuit if the bike ran well the day before these two vent lines were blocked?

    The tool from Motion Pro is something to be desired with tuning these bikes.

    Thanks for the replies. I know this subject has been beat to death.

    Any more insight would be appreciated but I plan on taking the IMS screws out a quarter turn then run the bike and repeat until the highest idle is achieved then will set the idle to its 1400 rpm.
    #5
  6. mcmann

    mcmann Motorcycle ADV enthusiast

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    Pilot jets plugging would only effect the idle. Maybe the fuel treatment loosened up some crap in the carb . . . Which partially plugged the side holes . . . Or not??

    #4 = low-speed jet (42)
    #5 = main jet (155/160) with the main jet holder
    #6 = starter jet (68)
    #7 = idle-air mixture control screw(2 1/4 turns out)

    [​IMG]

    Plan B . . . Spray carb cleaner through the top idle jet:

    #1 = main air jet (40)
    #2 = ACV (air cut valve) jet (80)
    #3 = idle-air jet (50)

    [​IMG]
    #6
  7. Fundy Rider

    Fundy Rider Where 2?

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    Thank you all for taking the time to help with your pics and all the info.

    I plan to start with the Idle air mixture screws after the tool arrives and if it doesn't cure the issue I will tear into it.

    I always tell everyone I live on the border of Calais Maine in the town of St. Stephen New Brunswick Canada.

    If Your heading to the East Coast of Canada wether it be Labrador Newfoundland or any of our Maritime provinces coming from the lower 48 states you will more than likely come through this border.

    The door is always open and if you want a tire or something I have an address stateside and could pick it up for you and you could do the deed at my place with a place to crash.

    Thanks again and I will let you all know how it goes once I have the tool.
    #7
  8. Boatman

    Boatman Membership has it's privileges ;-)

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  9. Fundy Rider

    Fundy Rider Where 2?

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    For sure with the carb boots.

    The hanging idle when the throttle is blipped is due to the vacuum and after a few seconds that is used up causing the idle to fall.

    I may be mistaken but there could be so many variables.

    Plan of attack is to start with the easy stuff and go from there.
    #9
  10. Fundy Rider

    Fundy Rider Where 2?

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    Well I went at it today and it turned into one of those frustrating days at working on our beloved bikes.

    The tool from Motion Pro was too long and then tried to make a tool but couldn't really see what I was doing and finally came to the conclusion I am going to have to take the carbs off to do this properly.

    Went online and found a few threads but I didn't feel too confident and felt they were missing a few things.

    Loosened up the top of the boots and looked around and thought man I need a female Asian hands to get at some of that stuff.

    Thought maybe I can gain some access if I manage to get them off the boots. The right side seemed quite cramped with wires and such. Thinking the tps was there so to be honest it intimidated me a bit.

    I read a few times that the cables tps and enricher can remain on. That would be ideal not having to mess with them.

    So I was wondering if any of you could help me out with a step by step to get the carbs off. After the carbs are exposed with just the bottom part of the airbox on and the two triangle doors open.

    I almost wanted to go to the dealer but another five hr ride and that would be taking the easy way out. I should know how to do this. I don't want to give up.

    Thanks again in advance.
    #10
  11. MortimerSickle

    MortimerSickle Semi-Adventurer

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    Not many steps left at that point.

    You should be able to reach in through the right-hand triangle to loosen the clamps on the carb boots- loosen only the top clamps.

    Disconnect the fuel line on the left side, below the airbox.

    Pull up with a rocking motion on the carb assy.



    I have found that a little silicone grease on the boots helps ease reseating the carbs. And, yes the hoses and idle-speed adjuster can be a pain to rethread through their holes in the airbox. :D



    After you have done it a couple of times, it is a pretty easy job, but is still time consuming.
    #11
  12. Orangecicle

    Orangecicle On a "Quest"

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    Once you have loosened one of the boot clamps on both carbs, grab the end of each carb and yank. Sometimes it works to rock one out before the other. Bend the sides of airbox out of the way as necessary to get the carbs past the lip. Now just twist the carbs over onto the sides and adjust the IMS screws. When putting the carbs back, MAKE SURE that you get the carbs fully seated on the boots.

    Finally, put the left tank back on, hook up the fuel line, and check to see how she runs. Repeat as necessary.

    And, go out and get yourself a set of FlexJet 2s so that you don't have to do this in the future: http://www.ktm-parts.com/RDFJ2.html#.UectqBY-I70

    [​IMG]
    #12
  13. StevefrmGV

    StevefrmGV MotoBro's RetroCycle's

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    Make sure your throttle cable are not hanging up. Happened to me once.
    #13
  14. Boatman

    Boatman Membership has it's privileges ;-)

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    My apologies for the tool not working. I know mine is a real tight fit but it's a few years old,,, maybe MP changed them.
    #14
  15. Fundy Rider

    Fundy Rider Where 2?

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    No problem. A honest mistake.

    Would the tps have to be set after things are sorted out again and if so how do you manage to get the voltmeter prongs up in the connector.

    It was set at the service but after messing with it I wonder if it will be out again.
    #15
  16. MortimerSickle

    MortimerSickle Semi-Adventurer

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    I didn't like the idea of stabbing probes through the seals and into the connector, so I unplugged it and ran jumpers to make the connection. I could then just clip onto the jumpers for the reading.
    #16
  17. ABuck99

    ABuck99 0.0

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    Good Idea!

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  18. Fundy Rider

    Fundy Rider Where 2?

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    Well went at it again today. I will try to keep it short and sweet.

    Easy enough to get the carbs off still connected.

    Found the front IMS at 2.25 and rear at 2.0. Set both at 2.25.

    Did start better but same issue.

    Set both at 2.5 and still same issue.

    Checked TPS and in specs off throttle and full throttle.

    Then I turned the IMS screws one more quarter turn to 2.75.

    It started with a lot more crispness and thought I had it. It hung at 1700rpm for some time.

    The fan came on at four bars and still there at 1700 and then up to five bars and then it fell again to around 1200rpm.

    There is something I noticed that happens every so often when the idle drops. There is and audible click and can feel something through the handlebars. It doesn't do this every time the idle drops but when it does it is as if someone hit a switch. The idle does drop without it as well and only when the bike is up to full temp will it drop.

    I maybe wrong but at 2.75 turns out on the IMS am I at the limit?

    To clear up what lines where blocked they are the two coming from each manifold. They were open before the service.

    Could it be just something clogged after they were blocked and the vacuum may have pulled some dirt from the lines.

    Now after today I think I could get through taking the carbs off completely and setting the tps after.

    Any ideas? Maybe seafoam before I rip the carbs apart(do I need to change the oil after a heavy dose?).

    If I do end up taking the carbs apart are there any springs or anything to watch out for. Same for the TPS and Enricher.

    If it wasn't for the forum no way would I have taken this on so thanks to all.

    I think I will take the KLR for a ride tomorrow and get back at it Sunday as I need a little mental break. Ten hrs at it so far and I am running out of hair to pull out.:huh

    Thanks again for all your time and patience with me.
    #18
  19. geometrician

    geometrician let's keep going...

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    this is an AIR pilot screw circuit. Opening it increases the air, not the fuel in the pilot circuit.

    generally (100% of the time?) the AIR pilot screw is on the engine (intake manifold) side of a carb body; the FUEL pilot screw is on the intake side of the carb body.

    If one had FCRs or TM flatslides it would be a fuel screw... our sucky old Keihin CVK's use the pilot screw for adjusting air mixture in the pilot circuit

    therefore opening (the number of turns out from fully closed) the AIR screw will allow more AIR in the mixture (lean)- not more (rich) FUEL.

    had to clear this up so our poor OP doesn't get (more?) confused & to prevent people mis-taking that statement as the correct one

    ---------------------

    and +2 on the FLEXJET II's. If you don't have access to a dyno with air/fuel ratio montioring then "seat of the pants" tuning is the norm. Flexjets allow you to ride the bike in a few seconds over the same stretch of road- which is where subtle (real-world) results are to be obtained.

    AND don't forget to check your air filter- when dirt builds up performance is affected- esp in the low/mid range RPMs (I know it was just serviced- but hey look at it)
    #19
  20. geometrician

    geometrician let's keep going...

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    :huh

    Fundy you aren't being quoted... not sure how you inferred all that. OC doesn't generally roll towards sniping at posters it's a helpful crowd here

    Only making sure that our terminology is correct- so that our diagnosis & solutions follow suit. In this case air & fuel are opposites when it comes to the pilot circuit adjusting screw & the effects on jetting/operation.

    KTM even got it "wrong" a few degrees by referring to these as "idle adjustment". It's the pilot circuit, not the idle circuit.

    And yes by the time you get close to 3 turns out you are reaching the limits of useful adjustment on the pilot screw. Better to go to a leaner pilot fuel jet.
    #20