What TW carb screw is this?
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Thread: What TW carb screw is this?

  1. #1
    Member eventiller's Avatar
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    I noticed that there appears to be a black plastic slotted screw in the side of the carb, can someone tell me what this seemingly screw shaped device is?



    I'm a "new" owner of a once southern machine, (a 1987 unit that is unmolested, all stock and original), and I need to adjust the air fuel screw, which I believe is still capped from the factory. I don't think this "screw" has anything to do with the air / fuel ratio, but its job has me puzzled.



    I'll post a pic with an arrow... hopefully it will show, sort of situated behind the short hose. Can someone tell me what its job is?




  2. #2
    Senior Member elime's Avatar
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    I bet it is a plug but I am just guessing.
    Long live the internal combustion engine!

  3. #3
    Member eventiller's Avatar
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    I'm thinking you're right.



    I've turned it... it doesn't thread out and it doesn't seem to thread in.



    I've had carbs from older bikes, (my first was a Yamaha TY250 from 1974), apart with no issues and not seen this type of plug / screw.



    Likewise, I've jetted carbs from modern day machines, (2007 and up dual sports like those found on the DRZ), and have not seen such a device.



    I'm rather interested in why Yamaha put it there and why it carries a screw slot when it doesn't seem to be in a threaded hole.

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  5. #4
    Senior Member Ayers Garage's Avatar
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    It is just a plug. I was looking at it a few weeks ago when I had the carburetor on my 92 torn apart.

  6. #5
    Member eventiller's Avatar
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    Thank you both gentlemen. I knew someone here would be able to help.

  7. #6
    Junior Member ppleasants's Avatar
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    I know this thread has been dead for quite a while but I'm trying to source this black screw/plug and I haven't had any luck. I wasn't observant enough and tried to drill out the plug because I couldn't remove it with a screwdriver and wanted to make sure I removed all parts while cleaning and rebuilding it (thinking that I could find a replacement without a problem). Well, I destroyed the plug and now it looks like my only option is to machine a new one out of some kind of plastic which isn't that difficult. If anyone has detailed photos of one of these plugs that they could post, it would be greatly appreciated. Measurements would also help. Does anyone know if this could be replaced with just a simple rubber or plastic cylinder without the flat end piece that fits in the slot in the slide?

    Thanks.

    By the way, I just bought an 89 TW200 that was caked in mud, hotwired, and covered in multi-colored spraypaint. I'm in the process of restoring the entire bike to an unmolested state by completely disassembling, cleaning, servicing, and stripping the rattle-can paint using acetone and some elbow grease to reveal the original paint underneath. Progress is coming along great so far and I'll try to start a build thread at some point

  8. #7
    Senior Member GaryL's Avatar
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    It is a blind plug! You don't need it because the orifice was never drilled. These carb bodies were used in other applications or sourced from them where this port might have been used. If it really bugs you just fill it with JBWeld and be done.

    GaryL
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  9. #8
    Junior Member ppleasants's Avatar
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    Quote Originally Posted by GaryL View Post
    It is a blind plug! You don't need it because the orifice was never drilled. These carb bodies were used in other applications or sourced from them where this port might have been used. If it really bugs you just fill it with JBWeld and be done.

    GaryL
    On my carburetor, this port opens into the center of the carburetor and the raised flat section at the end of the plug corresponds to the slot that runs vertically along the slide. If I'm not mistaken, the absence of this plug would lead to an increase in airflow into the carburetor and would adversely affect its proper function.

  10. #9
    Senior Member 1RobAusdemore's Avatar
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    Let's see some pics. I bought a 1992 in the same situation except it was all black spray paint. And the owner lived on a dairy farm and worked on a hog farm. I bet I found a pound of dirt caked under the gas tank when I took it off. I only took the bigger parts of the bike off. For the smaller parts I was cleaning I used S100 and a air hose, rinse and repeat on some areas, but it worked great for getting into the little areas fingers don't.

  11. #10
    Junior Member ppleasants's Avatar
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    Quote Originally Posted by 1RobAusdemore View Post
    Let's see some pics. I bought a 1992 in the same situation except it was all black spray paint. And the owner lived on a dairy farm and worked on a hog farm. I bet I found a pound of dirt caked under the gas tank when I took it off. I only took the bigger parts of the bike off. For the smaller parts I was cleaning I used S100 and a air hose, rinse and repeat on some areas, but it worked great for getting into the little areas fingers don't.
    Here's a shot of the engine the day I looked at the bike. Since then it's been completely disassembled. The carb was pretty dirty but after a thorough breakdown and soak in simple green, the parts cleaned up nicely.

    You can see in the photo that the slide is visible through the port in the side of the carb.

    IMG_3795_small.jpgIMG_3880_small.jpgIMG_3929_small.jpgIMG_3931_small.jpg

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