Valve Clearance question

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by Rethy, Dec 28, 2013.

  1. Rethy

    Rethy Been here awhile

    Joined:
    Feb 6, 2005
    Oddometer:
    120
    Location:
    Iowa
    A couple questions for those in the know. Recently acquired an 07 990 with 16K miles. Valve clearance checks made. 3 intakes okay. 4th is on rear cylinder @ .178mm little loose but suspect okay. Exhaust rears are both at the minimum allowance .25mm. Best I can tell KTM recommends 9K clearance check intervals. So my question is if I should address the 2 exhausts even though they are in spec. (minimum spec). I will check them again in 9K miles. Is it common to have much movement in 9K miles? If not I will leave them alone. Also is there much benefit in removing secondary butterflies. Seems like KTM went thru a lot of expense to put these on. Must be some reason but not sure why they are even on there.
    Thanks
    #1
  2. BigTony

    BigTony Been here awhile

    Joined:
    Apr 4, 2011
    Oddometer:
    329
    There is a link in the 950 how that gives part numbers for harley v-rod shims, which work fine on the 990, and they come in half sizes, so you could add some clearance and keep it in spec.

    I checked my valves at about 9, 16, and 24K miles and have had to shim each time. The last time was just the rear two exhaust valves and the others seemed to be holding. But anyway in my case they do seem to move a bit.
    #2
  3. Chuckracer

    Chuckracer Jerkus Maximus

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    Aug 26, 2007
    Oddometer:
    9,346
    Location:
    Lowville, NY
    Yeah, I'd open up the exhaust valves and get away from the minimum, but I wouldn't sweat the one loose intake. I'd bet in 9k miles they will be the same.

    In my case, three LC8's and only one needed touch up on a couple valves, and even that was me being anal. I've found them remarkably stable.
    #3
  4. Rethy

    Rethy Been here awhile

    Joined:
    Feb 6, 2005
    Oddometer:
    120
    Location:
    Iowa
    Thanks for the replies. I will go ahead and replace the rear cylinder exhaust shims. I will post my question on the secondary butterflies separately.
    #4
  5. Head2Wind

    Head2Wind MotorcycleMayhem

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    Mar 13, 2006
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    Location:
    NorthWet Washington
    and to make things interesting.... :D

    I intentionally set my valves on the bottom (tight) of the spec cuz I want as much lift/duration as I can get.... but that is when I am planning on being 'near home'. If I was running off on a very long term ride, I would set them to the high side of the clearance just to get as much service life without having to peal it apart somewhere in the world to check/set.

    I have found that these engines/valves are very stable and during intervals only change very slightly.
    #5
  6. Peanuts

    Peanuts Long timer

    Joined:
    Sep 12, 2009
    Oddometer:
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    Location:
    Beautiful but often rainy North Yorkshire, UK
    You may find that by turning the shims upside down the clearances go back into spec, this is because the valve stem wears a hole into the shim, the bucket is far wider so the shim sits a fraction thicker.

    The 250F is a bugger for doing this, the valve stems are smaller diameter than the LC8.
    #6