Question about 2003 Yamaha YZ 125

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My bike keeps leaking threw the over flow tube on the carb I have already changed the needle and seed and adjusted the float many times any suggestions

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Take your carb apart, clean and rebuild. As mentioned before, make sure there is no dirt or debris stuck in the throttle slide valve, but also check the shape of your needle valve. Replace the needle valve assembly if the tip is scoured or damaged. Lastly, make sure the floats are installed w/ the pins in the right position (towards the bottom of the float chamber on my RM 250). I made this mistake the first time I rebuilt my carb and gas would pour our the overflow as the needle valve never knew when to close.

Posted on Aug 28, 2010

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You've got something keeping your float stuck. Pull it and check the rod its mounted on for anything. Even a grain of sand could stick it. Then get yourself to an air compressor and blow threw the jets.

Posted on Jul 21, 2010

  • bra1nr0t Aug 28, 2010

    I had this same problem in my WR250. The fact is, the do not sell the seat separate of the carb. To resolve this I tried all the same steps to no avail. In the end, there were only 2 options. This is what worked for me. I bought a box of oversize Q-tips from walmart and a tube of lapping compound. I put the Q-tip in a battery op. high speed drill, put lapping compound on the tip stuck it in the hole and spun it for about 10 seconds. It took about five tries to get it to finally stop leaking. The only other option is to remove the seat, take it to a qualified machine shop and have them make you one. This option is not recommended though but as a last resort as it may be difficult to find someone that can do it perfect. I cannot stress enought the importance of perfect because any defect will prove fatal for the carb, and they are about $300 bucks for a new one.

  • bra1nr0t Aug 28, 2010

    One more thing to add to my previous comment. When using the lapping compound, do not get it on the walls of the seat, and clean the seat when your done so you do not damage the float valve.


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The bowl may need to be cleaned or the jetting adjusted.Thanks you for asking and I hope it helps.Please leave me a 4 thumbs up.

Posted on Jul 20, 2010

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Hi, Corey and the usual suspects are:
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2. There may be some debris or varnish between the mating surface of the needle valve and seat which also requires opening up the carb and cleaning with carb cleaner.
3. You carb float level setting may be incorrect. You have to know the float height from the manual and then have it adjusted. There is usually a small metal under the float which is used for float height adjustment.
4. Your carb float may be stuck and this usually happens when the bike is on its side stand and not used for a long time.

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That tube would be the overflow tube. Your carb float is sticking open and allowing fuel to flow in constantly. You need to take carb apart, clean needle valve, and inspect or replace carb float.

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Dear Craig,
Presuming that the carb is clean !
It seems that you have either set the float level incorrectly, or allowed the needle to become jammed. The float bowl should a little less than 3/4 full of fuel when the fuel is shut off by the needle and seat.
Check that the needle and seat are working correctly by blowing in the fuel pipe, and then closing the needle by hand. Check that the flow is stopped when the needle is fully raised.
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If the needle and seat work, then look at the float level.
Further check to see that the floats are not filling with fuel. If this is the case, then the floats will have to be replaced as most repairs are only temporary.
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