Strange looking intake

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Gustavo.Ramos, Oct 14, 2013.

  1. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    Got intrigued today when looking down at a mates KTM 990 (2006), the rear cylinder intake looked quite ugly, greasy/sooted.. plugs look fine, no complaints about driveability. He was dazzled, but i believe he never seen the throat of his bike, so anything would dazzle him...

    [​IMG]

    Anyone ever seen this before and figured :huhwhat could be the cause of it?
    #1
  2. DELTATANGO

    DELTATANGO Motorcyclist and Dog Walk

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    Valve too tight?
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  3. mjskier

    mjskier Been here awhile

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    Is the crankcase breather on the rear of the air filter?
    If it is, I can see where most of the crap would get sucked in the rear inlet.
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  4. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    Doesnt sound like, but worth checking

    No, stock setup, breather into the front & clean throat!

    Been searching about it and the closest i've found relates to bad injector, although the engine revs fine.
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  5. Sumi

    Sumi Long timer

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    Backfiring into the TB can lead to this. Actually this is the only thing I can imagine that gets carbon buildup inside there:) Didn't your mate notice backfiring into the airbox / cutouts / farts? :)

    Anyway.. check the seating of that TB (look for a torn boot) and if the vac. ports on the intakes are OK. (no torn vac. hoses for example)
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  6. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    Did i mention the guy is dazzled with the bike? :rofl Brand new to him...

    Took it for a spin and it doesn't feel like missfire, maybe with closed throttle engine braking there is some exhaust backfiring but can't really assure if there is into the TB's.

    Been once on the 950 with an intake torn boot and felt it, but not this time. Taking the TB's out.
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  7. Sumi

    Sumi Long timer

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    Well then maybe it's an old story for the bike which has been sorted out already and noone cleaned the TB since.. Poping on decel at the exhaust is normal ofcourse, and if you can't feel anything wrong while riding it / idling (a carb/tb backfire is quite noticeable), then I doubt you'll find anything out of ordinary if you pull the TBs.. But at least you can give it a good clean. Don't fix it if it ain't broken :pPPPP
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  8. StevenD

    StevenD Hmmmm, dirt!

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    the cause i dont know precicely but have seen it on more than a few bikes already. I recommend using some fuell additive once in a wile to keep things clean. Dont worry about it for the rest, as long as the valves are in spec.
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  9. Peanuts

    Peanuts Long timer

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    I have seen that before. As the SAS enters at the rear of the airbox I wondered if that could be causing it?
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  10. Boatman

    Boatman Membership has it's privileges ;-)

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    A friend bought a 950 a while back and had the same thing. Bike ran great with no issues but it bugged him. Valve check showed the intakes on that cylinder were tight. Since he corrected the valve clearances the intake is staying clean. Also noticed the bike was a bit smoother.
    #10
  11. keener

    keener Speed changes you.

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    Check the valve clearances just to be sure.

    Also it could be that someone put too much oil into the engine. In that case the crack case breather spits out some of the the excess oil over the front cylinder intake. Front trumper intake sould be very oily.
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  12. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    No SAS.

    Front intake clean as shown in picture

    :lol3

    taking the TB's out for clean, verify intake boots and check valve clearences. I'm pilling beer cases for these services :deal
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  13. DELTATANGO

    DELTATANGO Motorcyclist and Dog Walk

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    What about the reed valve on the smog thingy?
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  14. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    Not sure if you're talking about the vapor canister, it's a EU model so no such device.
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  15. ADVill

    ADVill Been here awhile

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    I'm kinda liking the too much oil thing right now. Easy to do if you fill it up cold.
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  16. MortimerSickle

    MortimerSickle Semi-Adventurer

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    This will probably only add to the mystery, but I bought a low mileage 990 that had weird deposits in the intake tracts.

    I never did see the throttle bodies of the bike it came out of, but the intakes looked like this:

    [​IMG]

    I brushed it out as well as I could, then ran it several thousand miles with carburetors. When I pulled it apart for my first valve adjustment, the intakes were clean as could be.

    I have seen similar pics posted, and often the condition is blamed on ethanol fuel. But, almost all of the fuel I use is E10. so I doubt that theory.
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  17. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    that would be my guess (fuel+ethanol) based also on previous issues seen around OC, but i'm not affected to that kind of fuel cocktail so can't add much.

    This one clearly (or darkerly) seem to be oil/soot deposits from missed combustion...

    Wether is a ongoing problem, or remnants of something fixed before, it's unknown..
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  18. MortimerSickle

    MortimerSickle Semi-Adventurer

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    I guess I didn't make clear that the deposits in my intakes went away while using ethanol fuel.
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  19. pdxmotorhead

    pdxmotorhead Long timer

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    I've seen that same stuff many times on alcohol powered dirt cars injection and intake and anything aluminum that gets near methanol, and it is then left to sit.
    A good alky fuel stabilizer will help. Most Sprint car owners "pickle" their Hillborn style injection with Wd40/Marvel Mystery Oil/inser fav oil here... after races, the Methanol attracts water and will badly pit aluminum in a very very short period of time, like a week!

    Remember E10 is a min value, I've measured E10 at 18% several times..

    Easy way to a dq at the track is un checked pump gas.. IN fuel limited race classes..

    Cheers
    Dave
    #19
  20. Gustavo.Ramos

    Gustavo.Ramos Long timer

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    New developments, after a longer and carefull ride finally noticed something not right.

    Engine idles fine, but with very small throttle openings when starting to move it will occasionally backfire into the intake. Once it stalled the engine though.

    Interesting how different riding styles can mask symptoms.

    Either air leak through intake boot of something wrong with the injector..
    #20