Pyns blog and Valve clearance

Discussion in 'Crazy-Awesome almost Dakar racers (950/990cc)' started by K6KTM, Dec 28, 2012.

  1. K6KTM

    K6KTM Adventurer

    Joined:
    Oct 10, 2009
    Oddometer:
    32
    Location:
    UK
    He's a busy chap at the moment so I put this to the forum......

    Quote "just to make sure they are settled and the clearances are set at their optimum for longevity. Intakes on the large side of the tolerance exhaust on the tighter side of the tolerance. This is from my experience with these motors that the intakes tighten up as the valves bed into the seats and the exhausts tend to loosen off as the carbon deposits on the valve and seat."

    Question for the people that have done the clearance on there 990 motors did you find the same, that the exhaust were on the large side so needed a thicker shim. I only ask because I'm doing mine at the moment and the exhausts are on the larger side so they could go larger still not tighten up?
    #1
  2. Steveman

    Steveman Been here awhile

    Joined:
    Sep 14, 2011
    Oddometer:
    471
    Location:
    Austria
    Cant confirm that, on my 990 all valves where a little tight. Usually one adjusts the valves to the biggest value inside limits. At least I do...
    #2
  3. MortimerSickle

    MortimerSickle Semi-Adventurer

    Joined:
    Dec 1, 2005
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    14,221
    Location:
    Rainville, Orygun, where moss is a road hazard.
    I have had the odd experience of having the front intakes slightly loosen, while all other valves slightly tightened.

    I remeasured several times to make sure of the gap, and unless I managed to mis-measure on my two previous valve checks, it has grown by .001 in. :scratch
    #3
  4. kamanya

    kamanya Andrew to most

    Joined:
    Jun 3, 2004
    Oddometer:
    1,447
    Location:
    Southern Tip of Africa
    Mostly static

    But...


    This is the journey that my valves have taken over the Km's.

    I only know their journey from the time my warranty ran out. The big fluctuations in the beginning was from my heads being reworked from a burnt piston and bent valves... The reversal on 3 of them @ the 25k mark I think was bad measuring.

    The last measurements may also have been out as I was swapping it out for a refreshed 990 and I was just curious.

    [​IMG]
    #4
  5. Peanuts

    Peanuts Long timer

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    Whats the story with the burnt piston and bent valves??
    #5
  6. kamanya

    kamanya Andrew to most

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    Southern Tip of Africa
    #6
  7. Peanuts

    Peanuts Long timer

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    Sep 12, 2009
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    Location:
    Beautiful but often rainy North Yorkshire, UK
    #7