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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.
 

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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.
 

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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
 

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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.
 

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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
 

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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
 

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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.
 

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... 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
 

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Thanks for the help guys. I should have said the float bowl gasket (I had it in my head I knew what I was talking about at least). Its the square-ish gasket that joins the float bowel to the upper section. I had a problem with removing one of the float bowl screws & wound up drilling it out. This may have caused the float bowl gasket to not properly seal the two halves.
 

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... This may have caused the float bowl gasket to not properly seal the two halves.
Make sure you have the flat side of the gasket with the ridge facing up, or you may get a leak.







jb
 

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Thanks, I confirmed the flat side is out. I re-adjusted the float (which was set much too high 12mm).



Does anyone know how restricted the pilot jet is supposed to be. The main jet was pretty clogged and did take a while to be able to get a thin wire through it. I can't seem to get even the thinnest of wires through the pilot jet though. I can just barely see light when looking through it. Not sure how small the opening is supposed to be. I've left it soaking in carb cleaner but still very restricted. Not sure if that's normal or not.





Make sure you have the flat side of the gasket with the ridge facing up, or you may get a leak.
 

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Ok, its been soaking all night & I've been working at it for a while. I'm a little concerned with bending it (also use 175 psi air). Just to clarify, is it the same diameter sized hole from the bottom of the pilot jet to the top of the pilot jet? If so then I suspect that something may have jammed inside as opposed to residual fuel. Thanks again for the help.





Thanks, I just wanted to make sure I wasnt going to cause a greater opening than its supposed to have. I have all the time in the world.
 

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The pilot jet hole is tiny. There are other small holes on the side, 2 opposite each other and 1 opposite 1 other.

 

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That's exactly what mine looked like BEFORE I got through with it.
Now the hole is much bigger. At least its only $6. Thanks for posting the picture, saved me from putting it all back together.





The pilot jet hole is tiny. There are other small holes on the side, 2 opposite each other and 1 opposite 1 other.

 
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