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So WHY are valve clearances so blasted important?

Discussion in 'XJ Technical Chat' started by bigfitz52, Jul 22, 2011.

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  1. Toomanybikes

    Toomanybikes Well-Known Member

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    Yes and the other end of bad is to much clearance and the cam is slapping the valve open and at high rpm it can actually spit the shim and BOOM hole in valve cover and it's over pretty quick!
    Way back in the day a few companies made titanium retainers and bucket for some of the twin cam Japanese bike to solve that problem of heavy valve train parts floating at higher rpm.
    Then you could run"big" cams with adjustable sprockets.
    Ducati solved the problem with Desmo valve gear, that pushes valves ( the size of a 426 Hemi) open and pulls valves closed.
    Only limit is rpm that can break things like crank and rods coming out of case without Pistons attached !!
     
    Last edited: Aug 29, 2016
    Toomanybikes, Aug 29, 2016
    #51
  2. Toomanybikes

    Toomanybikes Well-Known Member

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    And that creates no space for oil between cam and shim and with no oil cam will burn the lobe and result in cam failure as well
     
    Toomanybikes, Aug 30, 2016
    #52
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  3. OldFleetGuy

    OldFleetGuy Member

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    OldFleetGuy, Aug 30, 2016
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  4. cgutz

    cgutz Well-Known Member

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    Using the step by steps, I successfully checked and adjusted the valves on my '83 XJ550 myself this spring. If I can do it, just about anyone can.

    I bought the bike new, and had the dealer do the initial adjustment at 3K. I drove it another 21,000 miles before doing it this spring. One was critically out of adjustment, 5 were out of spec.
     
    cgutz, Aug 31, 2016
    #54
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