10% leak down test question

Discussion in 'Dakar champion (950/990)' started by wiseblood, Mar 21, 2015.

  1. wiseblood

    wiseblood Quid Quo Pro Supporter

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    So, I'm getting a 10% loss as shown by leak down test on my front cylinder. Leak is coming from intake valves.

    Any thoughts? Instinct is that it's time for a rebuild of the front head and valves, minimally. (Fyi, rear is only about 4-5%, and through the pistons.)

    This is a 2007 KTM 950 SMR with 21k miles.
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  2. Chuckracer

    Chuckracer Jerkus Maximus

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    I would ride it - hard - get it good and hot, lot's of rev's, lots of throttle, not idling around NYC...then check it again.
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  3. wiseblood

    wiseblood Quid Quo Pro Supporter

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    Engine was completely cold. Bike is very disassembled for 20k service. Question now is, do I take it MORE apart, or not? (The thought of putting it all back together to take it apart makes me sad. :lol3)
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  4. Chuckracer

    Chuckracer Jerkus Maximus

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    I wouldn't. If I recall correctly this engine was pretty gunked up from a leaking balance shaft seal blowing into the airbox, yes? Odds are good there's just a little crap on the intake valve seats from that.
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  5. Zuber

    Zuber Zoob Supporter

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    Ditto. 10% is no problem. Adjust the valve to the loose end of the range, put it together and ride it.
    #5
  6. charlie264

    charlie264 Long timer

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    :nod

    Take it for a long spin then recheck, could be just shit....if its still leaking borrow a scope.
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  7. wiseblood

    wiseblood Quid Quo Pro Supporter

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    I do have a borescope. I guess I'd stick it down the intake and see if I see debris on the valve seat?
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  8. wiseblood

    wiseblood Quid Quo Pro Supporter

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    I fixed the balance shaft a few months back, and have ridden at least a couple thousand miles since then.

    FYI, I've figured out (at least, pretty sure!) that my oil consumption is a leaky valve stem seal. on the rear cylinder:

    http://www.advrider.com/forums/showpost.php?p=26261174&postcount=37

    Irony is, the leak down test shows the rear cylinder as healthy (4-5% only). Front is the one which is a bit sketchy.
    #8
  9. ICERIDER

    ICERIDER Adventure Rider

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    Leaking intake valves, what with the cams fitted? Clearances ok?

    Do you know which valve?

    Remove cam. Take the piston to Bottom dead centre. Remove cam bucket and shims. Whack the valve stem a few times to re-seat. Cover everything so if it flies apart you don't loose bits down the engine. Re-check for leak.
    #9
  10. wiseblood

    wiseblood Quid Quo Pro Supporter

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    Both intake valves. Tested by putting a tiny amount of seafoam down the intake at TDC and putting compressed air into the cylinder again. Saw bubbles.

    Valves had clearance at TDC. Didn't bother measuring it yet, but it was > 0mm.

    Good idea about giving the valves a whack! Uhh... Tap. But, that's a good idea! :beer
    #10
  11. charlie264

    charlie264 Long timer

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    To positive a leaky valve, squirt a little petrol on each valve closed....if it drains away quickly.

    Open the valves and look for slight v warn grove....or a chipped/broken bit off the lip.
    #11
  12. halfcab

    halfcab Been here awhile

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    Don't worry about it for now on a none race bike. If you do notice any performance loss it will be at vary, vary low RPM.

    There could be a bit of carbon keeping a valve from closing. If/when it gets to 13-15% think about pulling the head (if leaking from valves).
    #12
  13. wiseblood

    wiseblood Quid Quo Pro Supporter

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    I did that test slightly differently. A small amount (half-capful at most) of seafoam, one valve at a time. Pumped air into the cylinder (still had the leak-down tester installed). Observed spray and bubbles coming up from the valve seat. Maybe a bit more on the left intake valve than the right, but both were bubbling.

    That will be on the valve, or on the head?
    #13
  14. wiseblood

    wiseblood Quid Quo Pro Supporter

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    If it IS carbon build-up, I thought I'd just share this video... pretty interesting! Don't know if I'd do it with the SMR, but.... :D

    <iframe width="560" height="315" src="https://www.youtube.com/embed/WdT4DPFXIkM" frameborder="0" allowfullscreen></iframe>
    #14
  15. charlie264

    charlie264 Long timer

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    I would say valve, since lead free fuel those valve seats are hard....valves need to be softer or would just shatter....

    Looks like that mover shifted some carbon through physically smashing it off....the guy works for a mower company that sells the stuff...I wonder how many have hydro-locked using that technique.....fooking the bearings.
    #15
  16. wiseblood

    wiseblood Quid Quo Pro Supporter

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    :lol3 You might have something there.
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  17. charlie264

    charlie264 Long timer

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    did you scope the valve
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  18. wiseblood

    wiseblood Quid Quo Pro Supporter

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    OK... An update on this thread!

    I'm still working (slooooowly :snore) on my 20k miles service. I've renewed the valve stem seals and adjusted the one out of spec valve on the rear cylinder, and it's all buttoned up.

    I finally removed the cams from the front cylinder, and two additional things came up which make me think maybe I should get the head & valves redone.

    1. I see some suspicious wear on the Exhaust cam journals
    2. Intake valve are in spec, but shims are oddly at the small end of the scale: 2.30 mm (All other valves on both cylinders are around 2.70mm)

    Add this to the 10% leak-down past the Intake valves, and it starts to paint a picture which I don't like. :uhoh

    Here's what I saw when I removed the cam bridge:

    [​IMG]

    Note the shiny bit of the journal? Especially on the right? Compare that with the Intake cam:

    [​IMG]

    Now, looking at the cam bridge. Note, Exhaust on the bottom, Intake on the top:

    [​IMG]

    Close up of Exhaust right side (which seems to be the worst):

    [​IMG]

    I have not yet been able to source some Plastigage to measure the clearances, but it seems like abnormal wear to me. Does anyone with more experience have any insights?

    Also... evidence of leaking intake valves:

    [​IMG]

    :webers :lol3


    Friend said today after seeing the above picture: "You have it this far apart and you aren't going to do the valve job? Kinda like swimming halfway across the Atlantic, figuring you can't make it, and swimming back." :fpalm
    #18
  19. wiseblood

    wiseblood Quid Quo Pro Supporter

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    Not yet, but I will this week.
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  20. loph917

    loph917 Beard Bros Racing

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    what bike are you putting that terrorflex on?
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