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Intermittent Leaky Carb

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So I have been chasing a carb that leaks off and on - more on than off on my 04 YZ250F. I have cleaned and cleaned and cleaned the carb. Im sure its clean. I have not replaced the float or needle. Sometimes tapping the carb helps. Im wondering if people have an opinion on how best to debug this. Should I simply start with a new float and needle? Testing the float by pushing it up with the float bowl off does stop the flow of gas but that doesnt mean its working when the bowl is on. I also floated the float in some liquid so I know there isnt a hole in it. 

It really only leaks when I stop the bike and the petcock is open so I could just live with it. I thought it just needed to be cleaned. I am also concerned about orientation of the Accelerator pump diaphragm. I wasn't quite sure when I reassembled it if I had it in the right orientation. Im not sure that would cause a fuel leak from the float bowl.

Any suggestions would really be appreciated.

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Replace float needle and set float height.
If continues, replace float.
Diaphragm should look like this.
IMG_4668.JPG

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Pull the float needle AND INSPECT.

If there is a wear mark on the rubber, replace it. Other wise it is fine.

INSPECT THE NEEDLE SEAT. If there is any wear mark or pitting  REPLACE IT other wise you are fine.

REMOVE THE FLOAT NEEDLE AND POLISH THE CAVITY AND NEEDLE BODY to remove the corrosion that is causing it to stick in the cavity.

That's all there is to it.

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I have had issues with the o-ring going bad on the seat. Just replace the valve and seat. About 20 buck. More than likely your issue. Mine started intermittent and soon gas was flowing out the overflow constant un less I shut it off.

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yee freakin ha!  I replaced the float needle even though it appeared ok. I checked the float height according to the service manual spec (8mm) and it was really hard to see but it did appear to be too large. I adjusted the tab on the float and both of those together seem to have fixed the issue.

Thanks all.

 

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