Leaky carb / leaky petcock
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  1. #1
    Junior Member Under Dog's Avatar
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    Last night I bought a '95TW. It's the first of it's kind of bike I've ever owned (dual sport/off-road). Looks great, runs good, puts a smile on your face - all that good stuff.



    However, when I woke up this morning, there was a puddle of gas under the bike... I checked the petcock and it was in the off position. However, I was still getting a V-E-R-Y S-L-O-W drip from the carb drain tube. So, I'm assuming in part I need to replace/rebuild the petcock as it clearly isn't shutting off the flow of gas. Is the petcock a known weak point? Are there better replacement options to the stock valve?



    Next, I need to determine if I just have a leaky carb drain screw or if my floats aren't sealing properly. Any suggestions on how to determine that? Or am I better off just replacing/rebuilding the float needle valve and drain screws...



    Thanks in advance!

    Doug

    Portland, OR

  2. #2
    Member praeses's Avatar
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    Petcocks and float needles are just part of the carburetor game. The good news is parts are typically cheap. This bike isn't any different than any other. They wear like any other, but they also can be eaten or gummed up faster if improperly stored. If you're comfortable working with carbs I would suggest acquiring (downloading perhaps) the shop manual and going through it regardless. As you said its the first of its kind that you own, you may not know if its running healthy or not and you may not know its history either. Not that I am trying to instill any fear, but if its running too lean/rich/not vaporizing correctly you could end up with engine damage in the long run. With your current situation if the float isn't sealing the gas overflowing would be washing down the cylinder walls causing excessive wear. Its no different for any bike, once again.



    The drain screw shouldn't leak regardless. If you have gas leaking out of the middle hose at the bottom of the float bowl, well its leaking and pretty easy/cheap to fix. It may be a seal or crud or just loose. I usually place some paper underneath the carb after doing any carb work so it shows the "splat" where it dripped so I know if and where to look. Some paper works better than others, especially those that lose their colour when gas hits it. The two overflow lines towards the back of the carb suggest the float is leaking. That is more commonly the case. If that is, I would suggest doing a careful inspection first, and if in doubt replace it as a kit. I think I got both the petcock (with pickup screens, etc) and float needle set (housing, o-ring, needle, filter) for $15ea from boats.net. I posted somewhere in here that their sister site has a 15% off deal that may come in handy.



    As for the petcock, if you carefully unscrew the faceplate on the side (I think its spring loaded, might be best to do when off the bike in a clean room) the diaphragm usually shows a line leading from one of the inlets to the outlet when it gets worn and/or eaten. Some gas is harder on it than others.



    If you're pulling it apart, I would highly suggest taking a good look at the jets, emulsifier (can't recall its friendlier name) tube, and needle. Please read through the two carb stickies (cleaning and tuning). The cleaning one isn't directly applicable as a few things are different but the pictures help out a lot. The shop manual's diagrams will be more applicable.
    2008 TW200 Yamaha luggage rack w/small el-cheapo JC Whitney trunk and large tool tube, Jimbo Shield, re-wired headlight, Blaster Shock waiting to be installed.

    1989 TW200 Work in Progress

    1994 ZX6E (rebuilt transmission, then rebuilt replacement motor, then rebuilt transmission in replacement motor, fun fun) large JC Whitney trunk fixed to the back of a computer chair re-welded to make a nifty luggage rack

  3. #3
    Banned qwerty's Avatar
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    It's 16 years old, probably spent several periods of time stuck in a corner. If it was mine, I'd pull the tank, ,ake sure it's clean. Then I'd remove the petcock, clean all the pieces, take it apart, look for any problems, then put it back together. Then I'd do the same with the carb. I'd especially check anything rubber or plastic for cracks, holes, hardening, or deterioration. I'd check all rubber parts including hoses and boots. I'd make a list of any parts of questionable quality and order them online. I'd also order an appropriate main jet or three (they're cheap) unless I lived at high altitude, and hit the hardware store for a washer to raise the needle. I'd also order a spark plug and an oil filter.



    While waiting for the parts to arrive, I'd do a complete service: lube, clean adjust, etc. I'd check all electrical connections for clean and tight. Definately take a good look at chain and sprocket condition. Check tires for any cracking or dry rot.



    When the parts came in, I'd do the oil and filter change, put in the spark plug, put the carb together and back in place, and ride the heck out of it.



    This is what I do with every used bike I buy, even Tdub, and she only had 712 miles when she adopted me.




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  5. #4
    Senior Member phazer's Avatar
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    i just encountered the very same problem, gas leaking from what appeared to be the bowl drain screw. what it really was , was the bowl gasket got a little trashed up when i put the bowl in a vise to remove a stripped out drain screw. even though i wrapped the bowl in a rubber sheet to protect it, it still got a little tear in it. i assumed the tear was just enough to let air get in and it must have let the gas trickel out. i changed the gasket and put in a new drain screw and the problem was solved. even if the gasket looks good replace it anyway. its only $5.95 at www.bikebandit.com and its a genuine yamaha part.

  6. #5
    Junior Member Under Dog's Avatar
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    Well... it's not the carb drain screw. Closer inspection shows it's leaking from a different hole/down spout on the carb. I don't have a manual yet, but am assuming it is some sort of carb overflow. So, I'm guessing the petcock needs to be rebuilt and then the float needle valve needs some attention too.



    Boats.net seems to be a common recommendation. Any other favorites out there?



    How about mods/upgrades? Are there any for the carbs that I should be looking at since I'll be in them anyways?



    Thanks again!

    Doug

  7. #6
    Banned qwerty's Avatar
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    Quote Originally Posted by Under Dog View Post
    Well... it's not the carb drain screw. Closer inspection shows it's leaking from a different hole/down spout on the carb. I don't have a manual yet, but am assuming it is some sort of carb overflow. So, I'm guessing the petcock needs to be rebuilt and then the float needle valve needs some attention too.


    Manuals are downloadable for free. Sticky in this forum.



    Boats.net seems to be a common recommendation. Any other favorites out there?


    www.stadiumyamaha.com has good service, but can nail you on shipping on small items. Shipping on big orders isn't bad. Be aware.



    How about mods/upgrades? Are there any for the carbs that I should be looking at since I'll be in them anyways?


    Order a couple bigger main jets when you order the other parts, pick up a couple flat washers from a hardware store or hobby shop (many sources don't have washers that small), and tune the carb properly using the instructions in the carb tuning sticky in this forum.



    Thanks again!

    Doug


    de nada




  8. #7
    Senior Member jbfla's Avatar
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    Quote Originally Posted by Under Dog View Post
    Boats.net seems to be a common recommendation. Any other favorites out there?


    I ordered a couple of jets from Stadium Yamaha. The shipping was a bit over $19. Never again.



    Try: http://www.ronayers.com/



    Flat rate shipping of $5. on most small items



    Good advice on doing a complete disassemble and thorough cleaning of an old carb. Try not to break anything or lose any parts.



    A likely suspect for the leak is the o-ring on the float valve seat.



    Manuals: https://tw200forum.com/index.php?/top...epair-manuals/



    jb
    2018 Triumph Street Twin..............2016 CB500F
    2014 XT250 ..................................2008 H-D Softail Deluxe
    2008 SV 650..................................2007 DR 650..

  9. #8
    Senior Member phazer's Avatar
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    i got my jets from www.jetsrus.com many sizes to choose from and i only paid about a buck for shipping. the trick is to call them to make the purchase. when you have the sales rep on the phone ask them to mail them in a plain envelope. they have generic and oem replacement jets. so far ive have very good luck with the ones i got from them.

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