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02 YZ250 Overflowing gas

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Hey guys, so I'm rebuilding my 02 YZ and I think I'm getting close to finished. Working on the fuel/air system, I installed new fuel/vent lines, rebuilt petcock, and cleaned out carb. I turned on the gas though and it started dumping out of the overflow lines. I dropped the bowl again and adjusted the floats and checked the sealing of the valve/seat by blowing through the fuel line. Right when, or maybe even a bit before, the arms are level, I couldn't even blow through it. I sealed it up and the damn thing kept peeing gas. Is there something the floats can be getting stuck on when I bolt everything together? I don't see any holes in the float and there wasn't any fluid inside. I didn't check if the valve seat oring was there, but it sealed up pretty well against me blowing on it. What am I missing? What else could it be? It just dumps fuel a couple seconds after turning it on and sitting on the stand. Should I just bend the tab up more on the floats or just see if they're binding somewhere?

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Same thing happened to me, do you have the needle clip on right? It could be that. I'm talking about the little silver bullet shaped thing that connects to the float tab.

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Same thing happened to me, do you have the needle clip on right? It could be that. I'm talking about the little silver bullet shaped thing that connects to the float tab.

 

 

Maybe a dumb question, but is the float bowl drain screw closed?  If so, adjust the floats down a bit more and try again.

 

The needle clip is the overlapping wires that hold the vlave right? I noticed that it bows out on one side. Does it matter the orientation for those bows perhaps? I seated it once and noticed that the wires weren't perpendicular to the float tab, so I took it out and spun the valve a bit and it lined up better. Wasn't sure if it had to be the other way around though.

 

The float bowl drain screw? That's the large 17mm? bolt on the bottom right? I pulled that and saw it had a good o-ring. No dumb questions, I'm a newb to this and anything that gets it fixed is a winner in my book :thumbsup:

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This is what I'm talking about, the clip just slides on the tab. Make sure it seats right. And is your pin that holds the float in, does it fall out right when you turn the carb side ways? Like its maybe to small, could also be the problem

This is what I'm talking about, the clip just slides on the tab. Make sure it seats right. And is your pin that holds the float in, does it fall out right when you turn the carb side ways? Like its maybe to small, could also be the problem

1380292137086.jpg

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The float bowl drain screw? That's the large 17mm? bolt on the bottom right? I pulled that and saw it had a good o-ring. No dumb questions, I'm a newb to this and anything that gets it fixed is a winner in my book :thumbsup:

Sorry, I'm a dummy.  That screw is on the FCR carb from my WR450 :bonk:

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The o-ring that sits under the float valve may be wasted. It can become cracked & porus and will let fuel flow past the valve even when the valve is closed.

You'll have to buy a float valve "kit" because the o-ring comes as part of the kit - seat, needle and o-ring.

 

Or you may be able to find a replacement o-ring at a hardware store.

 

Be sure to let us know what the final solution is. :thumbsup:

 

http://www.thumpertalk.com/topic/1043516-1999-yz125-overflow-fuel/?hl=%2Boverflow#entry11013545

 

http://www.thumpertalk.com/topic/599203-yz250-leaking-gas/?hl=%2Bleaking#entry5808000

 

http://www.thumpertalk.com/topic/640990-2002-yz250-leaking-fuel-from-overflow/?hl=%2Boverflow#entry6393438

 

http://www.thumpertalk.com/topic/943062-01-yz-125-leaking-fuel/?hl=%2Bleaking#entry9862876

 

 

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I dropped the bowl again and adjusted the floats and checked the sealing of the valve/seat by blowing through the fuel line.

 

What am I missing? What else could it be? It just dumps fuel a couple seconds after turning it on and sitting on the stand.

It only takes one hair to hold the needle off the seat. I had this problem last week w a small piece of grass.

My advice would be to back track and inspect the needle very closely (magnifying glass) for wear and look at the seat any fine dirt which you may have missed.

Edited by Swappa

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This is what I'm talking about, the clip just slides on the tab. Make sure it seats right. And is your pin that holds the float in, does it fall out right when you turn the carb side ways? Like its maybe to small, could also be the problem This is what I'm talking about, the clip just slides on the tab. Make sure it seats right. And is your pin that holds the float in, does it fall out right when you turn the carb side ways? Like its maybe to small, could also be the problem

Yeah I def have that clip on the valve, just wondering if it mattered which way the bows went. The pin does come out kind of easy but it still needs a good push to get it out. Float also doesn't seem to bind on it. I don't think that's it. Is there any way to check smooth float movement with the bowl tightened up?

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It only takes one hair to hold the needle off the seat. I had this problem last week w a small piece of grass.

My advice would be to back track and inspect the needle very closely (magnifying glass) for wear and look at the seat any fine dirt which you may have missed.

 

The o-ring that sits under the float valve may be wasted. It can become cracked & porus and will let fuel flow past the valve even when the valve is closed.

You'll have to buy a float valve "kit" because the o-ring comes as part of the kit - seat, needle and o-ring.

 

Or you may be able to find a replacement o-ring at a hardware store.

 

Be sure to let us know what the final solution is. :thumbsup:

 

http://www.thumpertalk.com/topic/1043516-1999-yz125-overflow-fuel/?hl=%2Boverflow#entry11013545

 

http://www.thumpertalk.com/topic/599203-yz250-leaking-gas/?hl=%2Bleaking#entry5808000

 

http://www.thumpertalk.com/topic/640990-2002-yz250-leaking-fuel-from-overflow/?hl=%2Boverflow#entry6393438

 

http://www.thumpertalk.com/topic/943062-01-yz-125-leaking-fuel/?hl=%2Bleaking#entry9862876

 

I do have a "various" kit from Autozone, but I doubt there is an oring small enough. I'll have to look at the seat and see if that ring is there. I kind of doubt it is though. Wouldn't it be odd that when the float is in the correct level I can't blow through it though? I was blowing pretty hard too and the seal felt solid. I'll take a look tonight.

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Pulled the float needle and not an oring to be seen. The needle itself has a rubber tip though and is in good condition. I did notice a bit of trash sitting around the seat. Cleaned everything up and adjusted the float to run a bit leaner. Checked it for shutting of gas flow while the bowl was dropped and it seemed to do fine. Bolted it up and it isn't peeing sitting still anymore. I'll see if it will idle tomorrow and run it for a day if ok. Can someone shoot me a picture of this oring? Either installed or in the kit or where it should be? Seems odd the needle would seat against rubber to me. Thanks! I'll be ordering up a new kit, just seems odd

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Yamaha part number 4MX-14392-00-00

 

The o-ring doesn't sit under the valve, it fits over/around the valve seat and creates a seal between it and the carb body. 

 

http://www.jetsrus.com/photos/photo_18_4729.jpg

 

http://www.jetsrus.com/needle_valve_float_bowl_gasket/needle_valve_by_manufacturer.html

 

It's a shame that the only way to get that o-ring from Yamaha is to buy another valve seat assembly, 'cuz quite often the valve itself is still good.  :banghead:

 

Thanks for keeping us updated.  :thumbsup:

Edited by CaptDan
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Yamaha part number 4MX-14392-00-00

 

The o-ring doesn't sit under the valve, it fits over/around the valve seat and creates a seal between it and the carb body. 

 

http://www.jetsrus.com/photos/photo_18_4729.jpg

 

http://www.jetsrus.com/needle_valve_float_bowl_gasket/needle_valve_by_manufacturer.html

 

It's a shame that the only way to get that o-ring from Yamaha is to buy another valve seat assembly, 'cuz quite often the valve itself is still good.  :banghead:

 

Thanks for keeping us updated.  :thumbsup:

Ohhh thanks a bunch for your great explanation! I completely misunderstood! Good thing I didn't try to stuff an oring where I thought it was supposed to be. I took her for a two hour ride yesterday and performed flawlessly! Started up first kick with no choke and idled for me just fine. Guess my oring must be alright :) I think it was a combo of a poor float adjustment and a wee bit of trash on the seat that was making it pee. Thanks for the help guys, she's a beast now!

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