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  1. #1

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    Plug Change In FX (4 Stroke) How to -

    For the guys who want to change plugs in an FX and have never done it ... or for the person that just wants to see where they are just in case.

    A few things ...

    The plugs must have anti-seize on the threads before installation. This reduces the galvanic corrosion between the steel plug thread and the aluminium alloy head material. Plugs stay in 4 strokes much longer and dont have 2 stroke oil floating round the combustion chamber to capillary up the plug threads.

    I've seen one FX that all 4 plugs snapped off in the head. The head had to be removed to drill out the plugs and helicoils were inserted. Bad news ! Expensive ! And totally preventable !!

    Yamaha specifies the torque setting with the coating of anti-seize on the threads simply by saying to use anti-seize and then giving a torque setting. For this reason I suggest using a good torque wrench to nip them up ... especially as they are only a 10mm thread.

    The torque setting is ... 13 Nm - 9.4 ft lbs - 113 inch/lbs.

    The anti-seize MUST be aluminium compatible. I use MolyKote brand but just check its compatible with aluminium with the manufacturer.

    I have some pics to go with method and will see how they post ? A moderator might want to clean it up if it goes a bit weird posting the pics ...

    Regards
    Anthony


  2. #2

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    Remove the airfilter box top by undoing the two centre scews and the 8 clips around the edge of the lid.

    Remove the airfilter.

    Next the coil plugs have to be removed. This involves compressing the tang of the plug on the coil (see pic). Depress gently and pull away from coil with fingers and plug should come off relatively easy if it doesnt dont pulll hard ..depress tang slightly further.

    Tang is shown in Pic 4 by the pen ! In Pic 3 you can see the coil plugs and the white collar that has the cylinder number on it.

    The plugs are numbered 1 through 4 they must go back the same way i.e. Coil 1 (front cylinder) gets plug No 1 etc ... to 4th cylinder.
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  3. #3

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    Next undo the coil bolt (10mm socket) This bolt has a locking compound on it called Loctite 572. I clean the coil bolts with acetone and a small brass brush and reapply the 572.

    The torque setting for the coil attaching bolt is 7.6Nm - 5.5 ft/lbs - 66 inch/lbs.

    Once undone you have to remove coils. Be gentle with them they are expensive. The coil has a rubber surround and grips the plug bores quite well. The way to get it out is to turn the coil in the plug bore anti-clockwise and then clockwise 1/8 th turn at a time while you lift it up. It will come up slowly ... and then out.

    We can now finally see the plugs !!! (smile)
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  4. #4

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    Next we have to make sure the plug bore has no crap in it ! Sometimes some tiny rubber bits from coil might be present. After plugs are removed I vacuum plug bore again to remove any matter from plug if some fell off. Usually doesnt but it doesnt hurt to NOT have anything go into cylinder !!

    I use a household vacuum cleaner that I tape a small piece of hose into the end. The one in the pic has two hose sizes for getting into smaller/larger areas. I keep it on the shelf and use it for various things. Start vacuum cleaner and insert hose down plug bore for a good suck out !!! Clean as then ... see plug bores in last pic !

    The plug spanner has to grip the plug because the bore is quite deep (5 inches or so) and you need an extension that is long enough as well. I use a Snap-On magnetic plug socket it grips the plug well ...traditionally a rubber boot type is used. Either is fine ... I do love my Snap-on though !!

    Pics ....
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  5. #5

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    Next remove plugs ...

    As I said remove plugs and vacuum again if necessary.

    I have inserted a pic of plugs on bench. The foreground ones are the ones I changed ... they have done 50 hrs and look great. The rear 4 are new ones, gap checked and anti-seize coated ready to install.

    Last pic is torqueing the plug. I torque it up ... undo and re-torque slowly til set and thats it !!

    Plug gap is .028-.031 inch.
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  6. #6

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    Coils go back in by reversing removal method. Pics of coils bolts dirty then with new 572 on them and a torque up of coil bolts.

    Plugs go back on coils ... in order please ... airfilter then cover ! Dont overtighten the airfilter box cover screws just firm is the go ... depress the lid with your hand (slightly) near the bolts as they nip up !!

    Plugs should be done every 100 hrs or annually and thats fine ... I do it 50 or six months just to remove and refit to keep threads lubed up.

    Regards
    Anthony
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  7. #7
    Moderator RX951's Avatar
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    Excellent Post !

    Thanks

  8. #8
    NZ Rider's Avatar
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    Thanks Riverdad great post. out of interest how many hours have been got out of the FX160HO's I've heard stories of 4,000hrs.

    Keith

  9. #9
    Moderator RX951's Avatar
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    Quote Originally Posted by NZ Rider View Post
    Thanks Riverdad great post. out of interest how many hours have been got out of the FX160HO's I've heard stories of 4,000hrs.

    Keith
    Welcome to the forum !

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