Carb nipple Identification help
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  1. #1
    Junior Member Tonto90's Avatar
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    I have the older style carb with 5 nipples above the bowl. And two an the bottom. I am on my phone and can't post photos but if someone can roughly tell me how to put the lines on I would be grateful. The two smallest nipples that are facing each other are connected with tubing. Leaving three to work with on top. One silver and two brass colored. I believe the one that is silver connects to the tank. Leaving the other two. Please help me out here, this is the only thing that is racking my brain about this bike!



    Dylan

  2. #2
    Senior Member FortPayne's Avatar
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    I was all excited about the description, turns out you were talkin' bout the carb...oh well.



    I'll go out to the garage and check but like you said, two are connected to each other; the large one is for the fuel, and the remaining are for venting the carb. Just run clear tubing from the nipples away from the carb. Some have run them up and others like myself just run them down with the carb overflow tube.



    Yup, just vents with generic clear tubing from Lowes.
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  3. #3
    Junior Member Tonto90's Avatar
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    Sweet so the over flow tube comes from the bottom of the bowl right? Is it next to the bowl gas release screw? So I have lines that running to nothing? Or am I thoroughly confused?

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  5. #4
    Senior Member FortPayne's Avatar
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    You are correct about them going to nothing. The overflow is not the drain coming from the drain screw its the other one. Lizrd on here posted the reasons for the vents one time (something to do with the venting) but I think the final conclusion was that they were useless. Have to keep tubing on them though to keep crap outta there. There is a handy loop to put them in at the base of the engine I think.
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  6. #5
    Senior Member mtkd's Avatar
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    Wouldn't say they are completely useless. I had a plugged vent line, and when I unplugged it the bike ran far better.
    -Szj



    2001 TW

  7. #6
    Junior Member Tonto90's Avatar
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    You guys are awesome, I am cleaning my tank right now just rebuilt the carb and installed it, put in a new battery in and the oil is clean and at the appropriate level. If Lady Luck is in my side by tomorrow I should have a running tw. For the cost of the battery and the carb kit. It's an 87 with 2000 miles that my neighbor wanted to get rid of so i figured I couldn't loose a whole a lot on this deal if it is a dud but if it works I might be the happiest college kid in town!

  8. #7
    Senior Member FortPayne's Avatar
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    Ahhhhh...the infamous 87. Could run forever, might die tomorrow. If you've read up on em then you know the cdi's are filled with gremlins, goblins, and the like. Good news is they still make them and it's an easy fix but they're a little pricey. Maybe you'll be lucky and have no trouble at all. Never hurts to have a spare cdi on hand.



    Go out and have a blast!
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  9. #8
    Senior Member lizrdbrth's Avatar
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    Quote Originally Posted by Fort Payne View Post
    You are correct about them going to nothing. The overflow is not the drain coming from the drain screw its the other one. Lizrd on here posted the reasons for the vents one time (something to do with the venting) but I think the final conclusion was that they were useless. Have to keep tubing on them though to keep crap outta there. There is a handy loop to put them in at the base of the engine I think.


    Carb vents aren't useless, but clogged carb vents are. Prolly the simplest way to deal with them on the early carb is to eliminate the plastic "Y" fitting and run two seperate vent lines to the bottom of the swingarm. Having them attached to the "Y" fitting means they're both capped off if the single vent line after the "Y" clogs.



    Some moron did a writeup on redoing the vent lines for water crossings. Might be worth a read down the road but splitting them up is the next best thing.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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  10. #9
    Senior Member FortPayne's Avatar
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    Im not big on water crossings myself (something about riding around with flooded boots turns me off to them) but I've been through enough to submerge the lines in question. Is there a chance of getting water in the carb or something of that nature?
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  11. #10
    Senior Member lizrdbrth's Avatar
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    When the lines get clogged or are submerged they lock up fuel flow. This is similar to a clogged fuel tank vent.



    My lame analogy. Applies to either the fuel tank or the float bowl:



    Let's take a gallon plastic milk jug. Fill it with liquid, then turn it upside down. What happens?



    Nothing, at first. Then shortly therefter there's a big "glug" and a slug of liquid comes out, then stops, "glug", more liquid, then nothing, and so on..



    Now take the same filled milk jug, turn it upside down, punch a hole in the bottom of it and all the liquid poors out smoothly. You have just "vented" your milk jug (fuel tank, float bowl). Fresh air is now coming in above your liquid, eliminating the vacuum condition within the jug.



    Except the mouth of your milk jug is quite large, whereas the fittings feeding fuel to your carb (or in the case of your float bowl, the idle and main jets) are quite small. If there's no vent or if the vent is clogged the "glug" never occurs and your fuel just sits in limbo unable to reach the exit.



    In water crossings the water itself clogs your vent lines. It's kinda like putting your thumb over the hole you made in the bottom of your jug. Most times if it's a quick crossing they don't stay clogged for long enough to stop flow. But if it's a long or particularly deep crossing and it occurs your engine stalls and you're screwt. In the case of the float bowl your engine will typically stall long before any meaningful amount of water can travel up the vent line. So stalling midstream doesn't neccessarily in and of itself result in a float bowl full of water. But hanging out midstream with a stalled bike with water above carb level or dropping the bike while you're wrestling it and the current will guaranty water in the float bowl, crank case, fuel tank, sleeping bag and alll your granola bars..



    Additionally, as long as that vent line is still submerged your float bowl will never get that gulp of air it needs to release the fuel to your jets. You can sit there in the middle of the stream kicking it all day if you wanna. It ain't ever gunna start.



    The cure for this is usually to "tee" the vent line so that one opening goes to the normal location below the swingarm and the other to someplace high on the bike, like under the tank. That way if the lower one gets clogged or submerged the float bowl will still get air through the vent higher up.



    The early carb has redundant vents, but Yamaha chose to run them into that "Y" fitting which essentially makes them a single vent again. Splitting them up increases the odds that one of them will always be open. Not as good as a hi-low vent, but quick and dirty.



    I can explain it to you, but I can't understand it for you.

    Powdercoated '87 frame, extended swingarm, YZ fork legs, ATV tire, 14/55, XT350 tank, spliced quick-release seat, disc brake conversion, beeg headlight, beeger rack, Lizrdcooler, Lizrdventz and bunch of other stuff all covered in invisible ink.

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