Carb Float Height?
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  1. #1
    Member tok-tokkie's Avatar
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    Petrol was leaking out of my carb when the bike was parked on the side stand. I had not had the carb off & am not aware of anything that would have changed the float setting. I have a 2009 with CV carb (2.5" black plastic cover over diaphragm).



    I have 2x removed the carb and checked the float valve. The rubber cone of the valve is perfect. The brass valve seat looks perfect. Remove seat, fit needle in and try to blow through & it seems to seal perfectly. With it fitted to carb it seals perfectly when blowing down the petrol inlet pipe & closing the inlet by lefting the float.



    The workshop manual I have lists the float height as 26 - 28mm (1.02 - 1.10"). The pictures show a different carb. When I measure my carb the float height is about 10mm. I don't find the float height specified in the TW Wiki.



    What should the float height be? Where do you measure it?



    EDIT: Have just read the beautifully illustrated Lazy Man's Teikei (TK) Carb Cleaning sticky thread which does not specify but implies i should just bend it a little.

  2. #2
    Senior Member uktw125's Avatar
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    To check your float height you can use a piece of clear flexible pipe. push the pipe onto the carb drain spigot on the bottom of the bowl and lift the other end up above the carb so it forms a U shape, then open the drain screw a little so fuel goes into the clear pipe. Now the level of fuel in the pipe should be about 2mm below the level of the bowl/carb gasket surface.

    Higher will cause an overflow, lower may starve you of fuel.

    Try to keep the bike upright for this.



    I hope that's clear, I'm not the best teacher I'm afraid.

  3. #3
    Banned qwerty's Avatar
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    Have you downloaded the supplement for the shop manual for the late model bikes with the newer carb?



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



    Page 39 of the supplement has the instructions for the procedure uktw125 described above.




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  5. #4
    Member tok-tokkie's Avatar
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    Quote Originally Posted by qwerty View Post
    Have you downloaded the supplement for the shop manual for the late model bikes with the newer carb?



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



    Page 39 of the supplement has the instructions for the procedure uktw125 described above.
    Many thanks. Downloaded the supplement. Page 45 says 10-11mm. Pictures are so much better in the supplement compared to my main Manual.

  6. #5
    Senior Member peruano's Avatar
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    There is a little O-ring on the float valve that can be compromised without showing it very evidently. I'd definitely try to replace that one. I had to go into mine twice to trigger on what the problem was. Good luck. Tom
    Tom - TW200 2002, Kawasaki VN 500 2006

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  7. #6
    Member tok-tokkie's Avatar
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    It could well be that peruano. I set the float height up an extra mm & still it leaks. Made a level gauge out of pneumatic nylon tubing & the level is way above where it should be. I now realise there has long been the small of petrol in the garage - I assumed it was the petrol transpiring through my Clarke tank (it bubbles the decal I have stuck on it).



    I have ordered a new needle valve assembly. When I pulled the seat out I thought that o-ring was a loose fit. I will take notice of the difference in resistance when I fit the new assy.

  8. #7
    Senior Member peruano's Avatar
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    Chances are your float valve has been leaking for a long time, but not much if you always turn off the petcock when you park the bike. I had the persistent smell of gas and eventually narrowed it down with an o-ring replacement. The reason the gas is not stronger is all that is leaking (or overflowing the bowl) is the amount of gas from the petcock to the carb (if the petcock is shut off). Good luck with the fix. Gas leaks in garages are bad news - especially if you have a gas water heater pilot lighted as I do. Tom
    Tom - TW200 2002, Kawasaki VN 500 2006

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  9. #8
    Junior Member jim1504's Avatar
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    Sorry for reviving an old thread. Would a mis-adjusted float cause a leak at the float gasket point on the carb. I checked the gasket and it appears to be intact and in good shape (except is does appear very flat). Thanks

  10. #9
    Banned qwerty's Avatar
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    It's really an o-ring, isn't it? Yes, o-rings will assume a square cross section over time. A ring with a square cross section needs to be replaced. By a new one from Yamaha, take it to an industrial seal supply, and ask them to match up the size and provide a half dozen or so in a material resistant to both gasoline and ethanol.




  11. #10
    Senior Member jbfla's Avatar
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    Quote Originally Posted by jimwil View Post
    ... I checked the gasket and it appears to be intact and in good shape (except is does appear very flat). Thanks
    If the o-ring looks like the picture on the right, it needs to be replaced.







    This is what could happen when that o-ring leaks (assuming the float height is set correctly):







    Yamaha only sells the o-ring as part of the float valve set.



    I have extra o-rings. PM your mailing address to me and I will send you one.



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

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