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Ummm, what are these?

Discussion in 'XJ Technical Chat' started by karljesse, Aug 18, 2013.

  1. karljesse

    karljesse Member

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    Ok, so 85 XJ700, Question, right where the valve cover meets the cylinder head, at the top of the fins, on the right side of the engine there are two rubber plugs. What are these? That is where I am leaking a little tiny bit of oil. I haven't done the valve clearance check yet, but that is at the top of my list.
    Anyway, I wondered if someone could bring me up to speed on this.
    Also what are the rubber spacers for between the fins? I know I have a few missing. Is this a problem?
    Thanks. You folks are the best!
     
    karljesse, Aug 18, 2013
    #1
  2. midnightmoose

    midnightmoose Member

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    Do you mean the two half moon shaped plugs? They are part of the valve cover gasket. The rubber blocks between the fins are vibration dampeners. They help prevent a ringing sound from the fins.

    Chacal has them...

    Cylinder Fin Insulators:
    OEM Yamaha rubber CYLINDER FIN RUBBER INSULATORS. These are the small, rubber, wedge-shaped noise absorbers that fit between adjacent levels of the cylinder head cooling fins at various places on the heads. Usually hardened or missing from original motors. Replacing these insulators with new ones really helps to quiet down an engine, and especially eliminates the fin "ringing" which can sound very much like valvetrain noise, while giving your engine that authentic, original appearance.
    HCP1840A OEM cylinder head rubber FIN INSULATOR, for the RH side of engine. Differs between models, but normally use 8-10 per engine on the right side. Fits all XJ550, XJ650, XJ700, XJ750, and XJ900RK models.

    HCP1840ASET10 OEM cylinder head rubber FIN INSULATORS, for the RH side of engine. Set of 10:


    HCP1840B OEM cylinder head rubber FIN INSULATOR, for the LH side of engine. Differs between models, but normally use 15 per engine on the left side. Fits all XJ550, XJ650, XJ700, XJ750, and XJ900RK models.


    HCP1840BSET15 OEM cylinder head rubber FIN INSULATORS, for the LH side of engine. Set of 15:
     
    midnightmoose, Aug 18, 2013
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  3. bikeboy929

    bikeboy929 Member

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    that's about the only 2 things i could think of, if that doesn't awnser it, maybe take a picture?
     
    bikeboy929, Aug 18, 2013
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  4. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    True. On the YICS motors they are molded as part of the gasket.

    If this is the first time the valve cover has been off ever (likely) you will need to replace the gasket, as well as the rubber/metal composite "donuts" on the bolts. Those donuts are what press the cover down against the gasket and head, as the bolts have stop collars on them that limit how far they can be tightened. If you replace the gasket and not the donuts, the new gasket will leak too.

    Once you've replaced the gasket and donuts, they can be re-used for numerous subsequent service cycles. The original ones are guaranteed to be baked hard.
     
    bigfitz52, Aug 18, 2013
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