04 YZ450 need help needle valve

6 replies to this topic
  • snowboardstylee

Posted February 21, 2009 - 03:37 PM


ok so i havent rode my bike in a while. and went to start it up today and ride it a bit , now as soon as i turn on the gas valve(petcock) gas starts pouring out the drain hose at the bottom of the float bowl(sucks) so im thinking maybe the needle jet is clogged or soemthing and is sticking the float or someting

anyone want to help me with a suggestion or where the needle valve is
or just some good ol help or suggestion would be wonderful its sat. and well not many places are open.


  • YZThumper07

Posted February 21, 2009 - 04:49 PM


To access the needle valve..just remove the bowl (bottom cover) from the carb. You will see the the float (black) immediately. The needle valve will be located towards the back of the float close to the point where the float pivots.

Inspect to make sure the needle valve is connected to the float as it should be, and moves up and down freely when the float is pushed up and down (just push the float up and down gently by hand) Gently push the float up to about level and turn the gas on..no gas should come out if everything is working properly. If it does i would take the needle valve out and check for wear around where the needle sits against the seat (up towards the tip)

If nothing else..clean the needle really well while you have it out and use a light blast of air to clean out the slot the needle goes up in. (careful not to blow the small o-ring out that's up in there), and see if that solves the prob... Hope that helps.. :lol:

  • snowboardstylee

Posted February 21, 2009 - 06:09 PM


is the needle valve that conical shapped thing that is connected to the float in the middle that goes up into that small round housing ? or is that something else?

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  • grayracer513

Posted February 21, 2009 - 08:20 PM


That's what it is, alright.

Download a manual:


  • XR133

Posted April 08, 2009 - 03:45 PM


Is it true that there should be an o-ring up in the needle valve housing? Mine doesn't have one and I don't see it referenced in the factory manual anywhere. I'm wondering if this isn't the source of my fuel overflow problem. Everything seems to be clean and adjusted correctly.

  • grayracer513

Posted April 08, 2009 - 07:48 PM


There is an O-ring that seals the needle seat to the carb body on '02 and older models that have removable needle seats. '03 and up have seats that are pressed in (no O-ring), and not serviceable.

  • XR133

Posted April 09, 2009 - 02:41 AM


Thanks Gray...I didn't see how an o-ring could possibly work in there ('03 450), but I wanted to make sure. Found the source of my trouble to be a large chunk of dirt in the fuel line just before it enters the carb body. Couldn't see it, but it finally broke loose with compressed air. I think the flow of gas was just enough to wash bits of it into the needle valve, preventing it from closing. All is good now, it appears.

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