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Thread: how to remove spark plug on 400EX?

  1. #1
    Join Date
    Oct 2002
    Location
    Los Angeles & Taiwan
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    149

    how to remove spark plug on 400EX?

    The spark plug on the 400EX looks hard to remove, do I need to take off the gas tank as well?
    Red 400EX

  2. #2
    Join Date
    Jul 2001
    Location
    Charlestown, Indiana
    Posts
    1,095
    you can do it with the gas tank on but it will be a tight fit. The easiest way is to remove the tank. Just use the supplied plug wrench and a screwdriver to twist it out. Just make sure that when you put your plug back in that it don't get cross threaded. I also add a little anti-seize to the threads of the plug. that way the water and mud don't rust it making it hard to come out.
    2003 Predator, Hiper rims, Kenda tires, PRM protection, Renthal bars with Spider Grips, Fox TRS w/rezzies, much more to come.

    1999 400 EX Hot cams stage , K&N filter, air box modw/outerwears, ,14 T front sprocket, Pro Circuit T-4, Works Triple rate w/o rezz, coustom made skid plate and a-arm gaurds. PRM bumper
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  3. #3
    Join Date
    Dec 2001
    Location
    The Beaver State
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    10,438
    The only thing you need to take off is the spark plug boot.
    I use a 3/8 drive 18mm deep well socket and the short extention.

    The stock tool is supposed to work too without removing the tank but I don't have it.

    Joe
    ATVRiders Janitorial Technician


    !!!!!DON'T FEED THE TROLLS!!!!!!

  4. #4
    Join Date
    Dec 2002
    Location
    Southern Michigan
    Posts
    92
    Yes it will come out without removing the tank with the stock plug wrench or a socket. the easiest way I found to do it is to shut off the gas and stand it up on end on the rear grab bar...makes it high enough so its not at a goofy angle to get in there and do the work. This also makes it easier to start it back in by hand so not to cross-thread it.
    2002 Honda 400EX
    --FMF Power Core 4
    --airbox lid removed, K&N air filter w/outerwear
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  5. #5
    Join Date
    Mar 2003
    Location
    NEWPORT,NEW HAMPSHIRE
    Posts
    282
    i put a vacuum hose down in there before i take out the plug to get the driedmud out. i don't want that stuff falling onto the piston.... that whole setup is wierd.



    Tom
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  6. #6
    Join Date
    Jan 2003
    Location
    Clarksville Tn.
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    2,494
    Very simple project (if you want to call it a project).Less than one beer in time.As said before make sure you get all the mud out.I would recommend adding some Die electric grease to the spark plug boot(squirt inside)if you haven't already.If you think that is hard try changing one on a Cannon Dale.
    Big B

  7. #7
    Join Date
    Sep 2003
    Location
    Mattoon, IL
    Posts
    10
    What brand socket are you guys using? The Craftsman deep well 18mm is too thick... and the Stanley ones out at Wal-Mart look too thick as well. They don't carry Popular Mechanix any longer.

    HELP!!!

    Up until now I've been a die hard Honda fan for fit, finish, and ease to work on... this has been a big disappointment for me.

  8. #8
    Join Date
    Jan 2003
    Location
    Clarksville Tn.
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    2,494
    You have got to be kidding me.You are complaining about Honda because your socket wont fit?I personally never could find a socket that would fit either,so I went to the Dealer and ordered a stock spark plug tool.Changing the plug is nothing to get worked up over,Do you NEED to change the plug?I ran the same plug for a whole season and more(Oct-June).
    Big B

  9. #9
    Join Date
    Sep 2003
    Location
    Mattoon, IL
    Posts
    10
    Originally posted by Bill Fuller
    You have got to be kidding me.You are complaining about Honda because your socket wont fit?I personally never could find a socket that would fit either,so I went to the Dealer and ordered a stock spark plug tool.Changing the plug is nothing to get worked up over,Do you NEED to change the plug?I ran the same plug for a whole season and more(Oct-June).
    It's a spark plug change... it should be straight forward. I shouldn't have to grind a socket down to fit, they should have engineered the fitment a bit better.

    I have always spoke highly of Honda... in fact I've done 4 swaps in their cars, auto to manual conversions, suspension swaps, clutch changes, entire fuel system swaps, OBD2 to OBD1 conversions etc... all in their cars... and everything was always straightforward. This is just not what I have come to expect from Honda... I'm just disappointed that they would design something this way.

    I could understand if it was a more complex component of the engine, but come on... it's a spark plug for Pete's sake. And yes, I DO need to change the plug.

    BTW... how much was the new tool?

  10. #10
    Join Date
    Jan 2003
    Location
    Clarksville Tn.
    Posts
    2,494
    I forget the price but I believe it was around $10.As for fit and design,they want you to use thier tool so you don't put a rachet and socket on the plug and over tighten it causing even more frustration.I'm not trying to get into an argument here I just think that a person like yourself who has hade so much wrench time on a Honda product would appreciate Honda designing a simple tool to save you a bunch of *****ing when you pull the threads out of the motor because of over tourqing the plug.
    Big B

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