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Fuel cap vent and..

Discussion in 'Yamaha 250cc In-Line 4's' started by ByzKnight, Nov 24, 2005.

  1. ByzKnight

    ByzKnight New Member

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    Guys,

    The recommendation to clear your fuel cap vent is often given in this forum. I've taken my cap apart twice now and cleaned it to a point where it is spotless. It actually stunk of rotten egg the first time! But, i can't seem to find the "vent". There are only four holes. Two for the screws, and two that seem like they are useless. I'm guessing one of them is the vent. One has like an orange background with a white surface in the middle, and the other is just a hole in the inner cap with a ballbearing inside (makes a noise as such). Either way, i cleaned them out with a bit of air. Is this all you can do?

    Also, inspecting my carbs i notcied that the rubber boots clamping together the top of the carbs and the air box ontop are falling apart, and the connection between the two is very loose. Can this affect performance? And if so, where can i find those little rubber connectors?

    Regards,
    Damien.
     
  2. FZR Dude

    FZR Dude New Member

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    Correct Damien, there is a little hole on the underside of the fuel cap. Wanna make sure that it is free to allow air in and out. Not sure about the ball bearing as I've never taken mine apart. I have a couple of spares so I'll check one out tomorrow.

    The rubber things you are talking about are called intake boots on the air box side, or rubbers. If any air is getting in to the carbs then you are going to have mixture problems. Call up a wrecker and see what they have. You can always measure them and go down there yourself and maybe fine some off a different make that'll work.
     
  3. ByzKnight

    ByzKnight New Member

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    Tim,

    Went looking for rubber/intake boots, and couldn't find any. I figured this isn't an issue because if anything, my bike is running a touch rich, and these boots, being a bit decayed would only let more air in, which would be noticable i guess.

    Your reaction to the ball bearing thing in the cap frightened me a little. I started thinking that it is clogged with a metal ball!! DOuble checked it, and there is no way of getting this tiny metal thing out of that tiny hole. I'm quite sure it's supposed to be there, may act as some sort of valve???????

    I have a new question though. My fuel cap actually sits a few millimeters above the tank cover, and silver ring thing around the cap ('88 2kr). I push it right down before locking it, but it does come up a bit all the time. Have i put the tank cover on too tightly, or is this normal? Can it affect performance that i'm not aware of?

    Thanks again,
    Damien.
     
  4. Ciaran

    Ciaran New Member

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    Mine does that too, I am fairly sure it is just the rubber seal trying to expand after you compress it with the cap. That ball could act as a one way check valve if the bike decided to lay on its side to stop fuel leaking out the overflow?
     
  5. raaqi

    raaqi New Member

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    I'm not sure what the difference between the models are, but mine is a 3LN II.

    I took the rubber vent out of mine tonight because I really don't think it's necessary. I don't have a fuel filter, and I doubt it will make much of a difference anyway. I ran this by my mech and he said it wouldn't create any problems, decrease fuel efficiency etc.

    Guide to cleaning fuel cap & air inlet/outlet valve:

    The Fuel Cap!
    [​IMG]

    Take out each of the 7 hex screws, the top and two bottom one's are longer than the rest.
    [​IMG]

    Open the cap and take out the inner screw, being careful not to drop it into the fuel tank.
    [​IMG]

    The bike without the fuel cap assembly
    [​IMG]

    The fuel cap
    [​IMG]

    Turn it over, and start by taking out the two screws either side
    [​IMG]

    Without the screws the locking mechanism falls off, don't forget the spring that will fall out!
    [​IMG]

    Without the lock on, four springs are exposed, take these off. Undo the two screws noted & LIFT off the metal piece that comes loose.
    [​IMG]

    You should now have this:
    [​IMG]

    Look at what's left of your assembly. See how the gromet allows air to travel within so that it can escape to or enter from the world?
    [​IMG]

    Remember that metal piece you took off? If you turn it over you will see this! The orange/white plastic thing is the inlet/outlet valve!
    See the tracks? That's where your gromet goes. This takes air to and from the world to the valve.
    [​IMG]

    Now with the valve out, you'll have two main peices.
    See how the tracks come together now? With the gromet in the middle.
    [​IMG]
    [​IMG]

    Now. Clean it all up. I removed the valve because I don't want it anymore.

    Put the gromet back on, put the locking mechanism back on, screw the two screws back on, place the four springs back on top, place the gold piece back on and you should have this:
    [​IMG]

    Take the spring, and the lock as shown. Place the spring between the round bit and the lock. With your fingers place the rest of the lock over the top. Hold it down while you put the remaining two screws in & test that the lock works.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    It should now be back together.
    [​IMG]

    If you wanted to take the big gromet off, you could have.
    [​IMG]

    That's it!
     
  6. FZR Dude

    FZR Dude New Member

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    Raaqi, That has to be one of the best walkthroughs that I have ever seen. Excellent Job!!!
     
  7. ByzKnight

    ByzKnight New Member

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    Well done! Impressive.

    Too bad mine's a 2kr with fuel caps that are soo different it's not funny. <!-- s:roll: --><img src="{SMILIES_PATH}/icon_roll.gif" alt=":roll:" title="Rolling LoL" /><!-- s:roll: -->

    There are no fansy plastic valves in 2kr caps. Or if there is, we can't access them. Also, the 3ln cap has about 4 more parts to it! Bizarre.

    Our vent is simply a hole under the cap, that you can't see from the top of the cap (other side).

    But i'm certain this walkthrough will help 3ln owners.
     
  8. Squog

    Squog New Member

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    Ok... followed Raaqi's instructions - all went well. Matter of fact - TOO well ;) kudos to Raaqi <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt=":D" title="Very Happy" /><!-- s:D -->

    Got the last two plates under/above the locking mechanism mixed up and it wouldn't lock!

    So... silly Squog decided to swap around those plates whilst sitting on the bike..


    plonk! out falls one of the screws.

    D'Oh!

    Don't want to start up the bike now because there's a spanner/screw in the works! stuck in the fuel filter maybe? That is IF I have one!

    If not... Oil sump?

    -Muzza
     
  9. FZR Dude

    FZR Dude New Member

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    Nope, it is sitting at the bottom of the tank. It is too big to leave the tank under any power other than you taking it out. Tie a magnet to a string and drop in down in there. Should be able to fish it out.
     
  10. raaqi

    raaqi New Member

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    Hehe thanks bro.

    I initially thought there was only one hole, one input / output for air. But when taking it apart I found two.

    Air comes in from outside the bike through a hole at the base of the fuel cap, there's a space in the gromet which allows air to get in. The air goes through this hole, into the inlet/outlet valve, from there it can enter through to the hole in the bottom of the lock mechanism and into the tank.

    Squog! You idiot! But guess what? You did what I did. I dropped the inner hex screw into my tank. I rode to work and back today, 50km without an issue. Your fuel is sucked in by two rods, so whatever you dropped in there will just be sitting at the bottom of the tank, you can fetch it out later. Don't fret dude.
     
  11. Squog

    Squog New Member

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    Ok I have one question regarding the whole fuel tank cap assembly...

    I found a little spring - here:
    [​IMG]

    Any idea what it's supposed to do?

    -Muzza
     
  12. raaqi

    raaqi New Member

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    Not sure what it does. I didn't even see that when I was taking mine apart. It doesn't seem to affect air flow so don't worry.

    I sprayed my entire assembly with wd40. To lubricate and clean. I took out my valve too, I don't need it or want it. Better airflow this way
     
  13. Squog

    Squog New Member

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    try now ;)

    -Muzza
     
  14. Squog

    Squog New Member

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    I know I shouldn't fret... but Magnet on end of string - no-go <!-- s:( --><img src="{SMILIES_PATH}/icon_sad.gif" alt=":(" title="Sad" /><!-- s:( --> Just sticks to the side walls of the fuel tank... gonna need a magnet on a stick or something... LOL or I could buy a new fuel tank hahahaha

    Thanks again Raaqi <!-- s:D --><img src="{SMILIES_PATH}/icon_biggrin.gif" alt=":D" title="Very Happy" /><!-- s:D --> I haven't actually started the bike since I cleaned out the gromet - but it's good to know how to do it <!-- s:) --><img src="{SMILIES_PATH}/icon_smile.gif" alt=":)" title="Smile" /><!-- s:) -->

    -Muzza
     

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