Help - Valve specs and temperature

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by folknride, Dec 11, 2012.

  1. ElRod

    ElRod 4

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    Jun 13, 2008
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    North Texas
    That's too funny......nearly word for word here at an H-D shop in Texas when I did my clearances last summer.
    #21
  2. uraberg

    uraberg whosaberg?

    Joined:
    Apr 21, 2009
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    Durham, NC
    Indeed. 15 degrees.
    #22
  3. EatinDirt

    EatinDirt WannaB Thumpin

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    Aug 22, 2010
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    The Desert
    Roll that baby into the cabin where its nice n toasty your wife won't mind.:evil
    #23
  4. Zuber

    Zuber Zoob

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    Yeah, do some extra work to get them all on the loose end of the range. It'll run better. 30k is a good time to do this because they don't change much from here on out.

    Honing them with sandpaper is only good for 0.001" (0.025 mm). You must start with 100 grit, then 200, 320, 500 and you may get only a small change.

    For temp changes aluminum head will change more than the steel valve stem. At cold temps the clearance will be smaller, the alum shrinks more and pulls the cams closer to the valve seat. But, when the bike is running, the parts don't have the same temp. The alum head will only get to 200 deg F, but the valves may go to 300 F for the intake and sometimes 1200 F for the exhaust. This will close the clearances, much more for the exhaust. That's why it has more clearance to start with.

    Humm, Kali. Doesn't suck much right now.
    #24
  5. markjenn

    markjenn Long timer

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    "Better" depends on what you're after. Wider valve clearances result in an engine with less valve lift and softer cam timing. This will tend to move the torque curve slightly lower in the rev range, but reduce high-end horsepower.

    - Mark
    #25
  6. folknride

    folknride Old Adventurer

    Joined:
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    Oddometer:
    710
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    Alberta, Canada
    Thanks for the advice guys. My fourth valve check/adjustment - you'd think I'd get faster :huh.
    With Harley shims I was able to set all the valves - intake at 0.13 - 0.14 and exhaust 0.27 - 0.28 - just below the loose end of spec.
    I go slow so I don't do anything :puke1 so the job, with oil change and coolant flush (replace with Engine Ice) and a few little tweaks like some new Doubletake mirrors spanned three days. When I read that folks do this in 4 hours, I think they must have different plastics than me - and don't get me started on throttle body removal and replacement. Don't get me wrong - I love my bike and enjoy my efforts at wrenching - but couldn't they have made some of this stuff easier to get at!

    Bike started right up and runs great - California here we come.
    #26
  7. Douf

    Douf Limey Bitch

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    Depending on the actual materials and the geometry of the valve train, if you do the math it looks as though the temperature difference could have made a few tenths of a thou difference, which - based on the actual clearance tolerance range - is possibly more than insignificant.

    http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

    It's a pity you didn't ask about the Engine Ice too :evil

    Douf
    #27
  8. Zuber

    Zuber Zoob

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    Markjenn is right. For most people, starting easier, idling easier, better throttle response, more mid-range is better running. Most won't notice a 'little off the top' to get this.
    #28
  9. Black Hills

    Black Hills Long timer

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    when looking for shims talk to the guys in the shop, not the parts counter. Locally the Honda/KTM dealer just trades me what I have for what I need (if he has them). the local independant shop charges me $5/ea. and I keep the old ones..
    #29
  10. keener

    keener Speed changes you.

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    Toronto, Canada
    Record the clearances and changes you made.

    Dont change the clearances significantly, you might get some surprises.
    #30