950 Carb Venting

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by danarone, Apr 16, 2009.

  1. danarone

    danarone Adventurer

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    I'm in the ptocess of doing a canisterectomy, and I am curious about carb venting. I got all the info from HOW and various posts and thanks all of you for such great information.

    As for venting the consensus is to use two separate lines from the bowl to the outside of ther airbox and terminate them in the V between the cylinders.

    My question is, is there anything wrong with keeping the factory Y setup that ties the two vent lines together inside the airbox, and terminate the outlet tube from the Y in the V between the cylinders?
    #1
  2. Johnf3

    Johnf3 Long timer

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    That works fine. Mine's been like that for 6k miles without any issues.
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  3. thugdog

    thugdog Druid Revisionist

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    #3
  4. Monty_Burns

    Monty_Burns Excellent.

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    I did exactly that and got a little bit of surge at cruising speeds. I redid it following the HOW and was happy with the results. To each his own though.
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  5. danarone

    danarone Adventurer

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    I'm thinking of using a short tubes from bowl vent to elbows in the side of the airbox under the filter area. These "snorkels" would be away from water and out of the wind, and easy to diconnect/re-connect for maintenance.
    Any thoughts?[​IMG]
    #5
  6. volrider

    volrider Been here awhile

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    One way to find out:D
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  7. SteveAS

    SteveAS Crank

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    I don't see any advantage over the usual, KTM-designed solution of 10" and 11" vent tubes terminating in the V of the engine. I've not heard of anyone having problems with water or wind with that configuration and it's even easier to deal with for maintenance than what your propose.
    #7
  8. Head2Wind

    Head2Wind MotorcycleMayhem

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    the 10/11" solution works, and works very well, especially if you are running a prefilter. correct bowl venting is critical for that last little tweak when it comes to these sensitive carbs.

    as far as your idea of sending the vents out the side, that might work OK so long as there is not a loop that would trap liquid fuel in it and not allow it to drain back into either the carb or out to the ground.

    same goes for the tank vents. if there is a low spot for liquid to accumulate and lay in, thus not allowing full/free venting you will experience problems.

    directly from my experience with quite a few 950s, I have suggested and helped resolve several bikes with a slight surge problem by changing the vents from the Y to the singles.

    ya, I got 2.5 hours of sleep last night so.... not sure if I can make that clearer....
    #8
  9. danarone

    danarone Adventurer

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    Thanks all for the input. It seems like the options are a Y with 1" sticking down under the airbox, or 10" and 11" separate lines. I'll fiddle with those options and keep it simple.

    Worth noting...my bike already has a very slight surge/hesitation, and I haven't changed anything yet. I'm hoping the canisterectomy will eliminate this issue. :confused I'll let you know.

    Now, I do have another question...:eek1

    Anyone know what the vacuum line that goes to the SAS valve does? I'm assuming it opens the SAS valve at certain RPM's and introduced fresh air to the exhaust. I want to keep SAS to avoid Cat problems.

    Should I start a new thread for this?

    [​IMG]
    #9
  10. Pete156

    Pete156 I love to eat!

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    Get rid of the Cats, they're very heavy and do nothing but turn the bike into a garage furnace.
    #10
  11. uk_mouse

    uk_mouse Aquatic adventurer

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    My experiences on SAS and cats ...

    1 - Removing the SAS will not cause the cats to "clog up". I ran with no SAS for 10,000 miles, then I cut the cats out of my pipes, they were clean as a whistle no evidence of clogging. Of course they may have been rendered inoperative in some way, but who cares?

    2 - Removing the cats from the standard pipes does not make them run appreciably cooler. As noted above I cut the cat out of my pipe (I'm using a single silencer with a 2-1 pipe) and it's still frigging hot. It may be slightly less frigging hot than when the cat was in there but to be honest, if your skin is searing off you don't care about a few degrees either way :)

    The standard cans get so hot mainly because of their construction - thick double skin steel which holds the heat, and a convuluted gas path that allows more heat to transfer into the metal. All the aftermarket cooler alternatives are made from thin aluminium or titanium which don't hold the heat nearly as much.
    #11