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xj550 cam shaft clearance - tapping noise.

Discussion in 'XJ Technical Chat' started by fatnfast, Jul 29, 2014.

  1. fatnfast

    fatnfast Member

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    Following on from my earlier reported top end tapping/knocking noise I finally had time today to have a look.
    As I suspected the clearance identified by the Yamaha service note is excessive on the exhaust side, which is exactly where to noise comes from.
    [​IMG]

    Heres a 0.08mm feeling going in, and indeed a 0.10mm gauge just about slotted in as well. Max clearance should be 0.076mm.
    [​IMG]

    So whilst Yamaha say this will not affect the engine and is just a customer relations exercise, It would be nice to correct it.
    However, the replacement cam cap is no longer available. I do have a spare set of caps which were sent to me with some spare cams that were to cheap to not buy. Im aware that the caps are machine to suit the head, but does this apply in light of this issue to the inner cap?
    So:

    Could I use the spare cam cap I have? This is from a latter 550 maxim.

    If so can I just remove the cam cap in question and replace, or is there a need to loosen the cam chain and camshafts in order that the bolts can be retightened in the correct sequence?

    Or should I adopt 'don't touch if its not broken' approach and just button her back up?

    Any advice would be great :D .
     
  2. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    1. Re-read the very last sentence of the page again.

    2. If you decide you REALLY want to replace it, get some plasti-gauge and have at it. The cap is aluminum and will quickly adapt to the new cam if there's a spot of tightness......the cam won't wear down, the aluminum would wear. But the plasti-gauge would show you what you're really looking at.

    Have you double-checked to make sure that you're exhaust collars are all nice and tight? A single loose collar can create an exhaust leak that sounds like the engine is falling apart, a sparkplug fell out, a cylinder went bad, or any number or heart-clenching sounds.......

    Dave F
     
  3. fatnfast

    fatnfast Member

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    Thanks Dave.
    I have re-read that last sentence a few times. Its just curiosity, but they do say 'curiosity killed the cat' so maybe I should just leave it.

    Its definitely not from the exhaust. 100% certain on that one.

    The frame/chassis number is very low and its only covered 24k miles. After recently adjusting all the valve clearances, possibly for the first time in its life, I think it has just highlighted the clearance noise to me.
    Double checked the valves just now and all are in the middle of the specified range.
     
  4. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    ok. Re-read that last sentence again. :)

    dave
     
  5. fatnfast

    fatnfast Member

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    Read that enough thank you.
     
  6. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Before actually swapping caps, measure the overall "width" of the intended replacement cap and compare it to your original. If they're the same, your "later" head doesn't have the modded caps and there's no need to switch.

    You shouldn't need to "Plastigauge" the journal, those inner caps are "dummies" to align the cams and provide a hold-down for the cover bolts, they don't have a cam bearing surface IIRC. If I remembered wrong and there IS a cam journal there, you'll need to check the cap-to-cam journal clearance with Plastiguage.
     
  7. fatnfast

    fatnfast Member

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    Thanks Fitz, thats good advice.
    Im just happy the noise is not impending doom ;-) .
     

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