Carb Issue on Yz250f

iudi2006
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10/11/2010 5:23pm Edited Date/Time 1/26/2012 12:29am
So my yz250f is having some carb issues. The carb will always easily get flooded and whenever i the turn the gas on it just leaks a lot of gasoline. Do you guys know what the problem probably is?
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iudi2006
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10/11/2010 8:35pm
Bump? I'm trying to go riding tomorrow and still have time to try to fix it.
TerryK
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10/11/2010 9:33pm
Sorry, I had a response all typed up for you hours ago but got busy and lost it lol.

Sounds like you have a stuck float needle. The easiest thing to try first is:

turn the gas on and then rap repeatedly on the float bowl with the plastic end of a screwdriver. This will sometimes dislodge any dirt that may be keeping the needle from seating.

If this doesn't work then you have to either rotate the carb enough so you can get at the float bowl screws, or take the carb off. Take off the float bowl and give it a good cleaning with an aerosol can of carb cleaner. Spray the needle/seat area while moving the floats up and down. this should dislodge any dirt particles that may be causing the problem. Be VERY careful you don't bend the floats.

Try the screwdriver thing first and get back to me.
mx5471
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10/11/2010 9:59pm
You have something in the seat of the float needle. A little grain of sand is enough to do it. Or the rubber on the needle is deteriorated and not seating properly,which isn't too likely,or possibly it could be damaged. That float needle is the shutoff for the gas when the tank valve is open. It allows gas to the carb bowl to be used by the engine,and regulates the amount of gas in the bowl. Try tapping the side of the carb bowl with a metal wrench softly several times. If that doesn't work then you have to remove the carb so you can flush it with carb cleaner. If you have to do that,remove all the rubber o-ring type gaskets from the bowl and the top of the carb,as they will swell if sprayed with carb cleaner,and be unusable. That's your problem. Easy to fix and free.
iudi2006
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10/12/2010 12:24am
Alright, Thanks to both of you guys for the help. I tried doing the screwdriver thing and it didnt work, turned on the gas and it leaked the same way. So tomorrow or today shall i say i'll take the carb out and do what you guys told me. So worse case scenario i'll have to change float needle right? Thanks for the help.

The Shop

TerryK
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10/12/2010 4:38pm Edited Date/Time 10/12/2010 4:40pm
Funny, didn't I just say that??



Don't use a metal wrench!! BTW, if you read what I originally wrote you notice that I said the gas has to be ON when you tap the float bowl. That way the dirt can be flushed out with the flowing fuel.
iudi2006
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10/12/2010 7:04pm
TerryK wrote:
Funny, didn't I just say that?? Don't use a metal wrench!! BTW, if you read what I originally wrote you notice that I said the gas...
Funny, didn't I just say that??



Don't use a metal wrench!! BTW, if you read what I originally wrote you notice that I said the gas has to be ON when you tap the float bowl. That way the dirt can be flushed out with the flowing fuel.
I used the rubber end of the screwdriver. And i'll go try it with the gas running and get back to you. Thanks again.
iudi2006
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10/12/2010 7:58pm
So i tried it out. For the first few minutes everything went great and it stop leaking and it didnt flood. Then about 3-4 minutes later it just started leaking again. I'm guessing i'll have to change the float needle.
TerryK
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10/12/2010 9:44pm
iudi2006 wrote:
So i tried it out. For the first few minutes everything went great and it stop leaking and it didnt flood. Then about 3-4 minutes later...
So i tried it out. For the first few minutes everything went great and it stop leaking and it didnt flood. Then about 3-4 minutes later it just started leaking again. I'm guessing i'll have to change the float needle.
Sounds like you have dirt in there still. Take the fuel line off the carb and let some gas run into a white or clear container and see if you have any dirt or spooge in the fuel.
iudi2006
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10/12/2010 9:51pm
iudi2006 wrote:
So i tried it out. For the first few minutes everything went great and it stop leaking and it didnt flood. Then about 3-4 minutes later...
So i tried it out. For the first few minutes everything went great and it stop leaking and it didnt flood. Then about 3-4 minutes later it just started leaking again. I'm guessing i'll have to change the float needle.
TerryK wrote:
Sounds like you have dirt in there still. Take the fuel line off the carb and let some gas run into a white or clear container...
Sounds like you have dirt in there still. Take the fuel line off the carb and let some gas run into a white or clear container and see if you have any dirt or spooge in the fuel.
I just turned on the gas about 2 or 3 times and just left it there for a couple minutes each time and it seems like it's not leaking anymore. Hopefully my problem is solved, but if not thank you so much for helping me find my problem.
10/13/2010 5:23am
When you turn the gas off and disconnect the fuel line from the fuel tank does the petcock leak fuel? I have seen several yamahas that leaked fuel after the petcock was turned off. The rubber gasket in the petcock gets torn and that piece of rubber travels down the fuel line and into the backside of the seat that the needle goes into. It is possible that is why you are having intermitant problems with it. You will have to blow compressed air back through the seat where the needle goes and see if anything comes out. Blow it out into a clean shop rag. This is most likely only the problem if the petcock leaks while in the off position though.
iudi2006
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10/19/2010 7:19pm
Alright so i have taken the carb out today and tried seeing if the problem was with the float needle. It wasn't,the needle looked brand new and i also cleaned out some of the dirt in there. Then close it back up and put it on the bike only for it to leak even more. Any more suggestions on what the problem could be.
10/20/2010 6:02am
if fuel is leaking out the overflow hose on the carb you have got something holding the needle and seat open ie the float is not shutting the fuel off. At this point I would suggest taking it to a professional and have them go through the carb and fuel system.
iudi2006
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10/20/2010 11:23am
if fuel is leaking out the overflow hose on the carb you have got something holding the needle and seat open ie the float is not...
if fuel is leaking out the overflow hose on the carb you have got something holding the needle and seat open ie the float is not shutting the fuel off. At this point I would suggest taking it to a professional and have them go through the carb and fuel system.
Would you know an estimate of how much it would cost to get it fixed? $100,$200?
10/20/2010 11:29am
I usually charge $90 for a carb clean here at Privateer Connection. However I am on a the east coast so it may be alittle more on the west coast.
RACEGUY
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10/20/2010 7:07pm
It's usually called a "float-valve assembly" and includes the stainless needle and the brass seat. Do not replace either individually.

You often can't see the groove worn into the "needle" with the naked eye, especially with neophrene coated needles. You also have no idea if a piece of persistant grit has worn a groove into the brass seating area.

Another thing to consider is a perforated float which fills with fuel and sinks, causing the needle to allow fuel to pass through even if the float bowl is full. For this test, very carefully remove the float assy and shake it next to your ear to see if you hear ANYTHING. The second step is to sink it in a gasoline-like fluid (put it in a jar and hold it down under the fluid level with something that will keep it submerged overnight). When you remove the weight, if the float doesn't shoot to the top, be suspicious. Don't forget to shake it and have another listen. PLEASE, try to avoid gasoline for this, and even if using alcohol or bulk brake-clean, put the beaker/jar outdoors and away from anything flamable.

Order a new float valve assy (OEM) but see where this all takes you and what it can teach us. Then, share it here.
iudi2006
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10/20/2010 7:52pm
RACEGUY wrote:
It's usually called a "float-valve assembly" and includes the stainless needle and the brass seat. Do not replace either individually. You often can't see the groove...
It's usually called a "float-valve assembly" and includes the stainless needle and the brass seat. Do not replace either individually.

You often can't see the groove worn into the "needle" with the naked eye, especially with neophrene coated needles. You also have no idea if a piece of persistant grit has worn a groove into the brass seating area.

Another thing to consider is a perforated float which fills with fuel and sinks, causing the needle to allow fuel to pass through even if the float bowl is full. For this test, very carefully remove the float assy and shake it next to your ear to see if you hear ANYTHING. The second step is to sink it in a gasoline-like fluid (put it in a jar and hold it down under the fluid level with something that will keep it submerged overnight). When you remove the weight, if the float doesn't shoot to the top, be suspicious. Don't forget to shake it and have another listen. PLEASE, try to avoid gasoline for this, and even if using alcohol or bulk brake-clean, put the beaker/jar outdoors and away from anything flamable.

Order a new float valve assy (OEM) but see where this all takes you and what it can teach us. Then, share it here.
The float doesnt seem to be the problem. It seems to be working fine. The weird thing is before i even took out the carb and opened it i did the screwdriver test and it stoped leaking. Then the next day i started it up and it was leaking. So it's a mystery. My local mechanic said that the seat on this carb is irreplaceable so i would have to get a new carb if it still leaked after they try to clean the seat out. If i have to get a new carb im fucked.

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