03 yz450f fuel coming from over flow tubes on carb.

ok to begin with the on/off switch is not capable off turning off the fuel but i put a in line fuel switch on the hose from the tank to the carb. im thinkin it cant be the neddle because it doesnt flood out even if its not running but any time the inline fuel switch is on the fuel starts pouring out. i think its coming from the hose that runs out the buttom of the the bowl on the carb. i dont know whats wrong. its the first thumper i have owned but i have had many dirtbikes and atvs so im kinda experienced on carb work. its not just when the bike is leaned over really far either it does it any time the inline switch is on. please help me and thanks ahead of time.

TJ

TJ -

It sounds like your float/fuel shut-off assembly isn't working properly. There could be any number of causes, from a punctured float to dirt between the needle valve and seat (don't confuse this with the jet needle that projects from the base of the slide).

You'll need to remove the float bowl to determine the cause. Let us know what you find or if you have any questions once you get in there.

:worthy:

... any time the inline fuel switch is on the fuel starts pouring out.

There are only two possibilities. Either the bowl drain is open (3mm Allen screw at the bottom of the bowl on the left side), or the float needle is not seating. The needle may be either damaged or dirty, orthe float level may simply be wrong.

or the float needle is not seating. The needle may be either damaged or dirty, orthe float level may simply be wrong.

Yep, or you could have a damaged or stuck float preventing the needle from being seated. There are a number of possible root causes for the incorrect condition.

TJ- look for what gray has suggested and then the reason for that condition (if possible to determine).

First identify the incorrect condition (open drain screw, needle not seating, etc) and then the reason/root cause for it being incorrect (dirt, damage, wear, misadjustment, etc). :banana:

First the "what" and then the "why". :worthy:

Hope it helps.

:banana:

I had a similar problem 2 weeks ago. When I turned on the fuel it poured out. I figured it was a stuck float/needle. Tapped on the carb, no change. Took the bowl off and found the needle was stuck, it looked corroded. I freed it up and all was good.

3 days later, at the track, it started and then soon died. Took bowl off again. this time it was stuck in the opposite position.

This time I figured I had water in the fuel, so I removed the tank and completely drained the fuel from every where and dried everything out with compressed air.

Haven't had a problem since. I think I had a little water in the tank that was corroding the needle and making it stick.

tried to remove bowl and the last owner apparently striped one of the screws. this seems to be common with carb screws. specially the bowl screws.lol. i will have to borrow some needle nose vise grips to remove it. ill let you guys know as soon as i get it loose.

ok so i cleaned the needle seat and its working perfectly now. problem is that when i tryed to restart it i flooded it by accident and it wouldnt start. i tryed to remove the plug which by the way wasnt fun. i took off the gas tank and got to the plug and couldnt get it out cuz of the frame bein right over top of the plug hole. does anyone know of a good tool to use. and then i gave up and put every thing back in place. i kicked and kicked and then it fired once and so i drift started it and got it to start. it was running fine and then about a minute later it started sputtering and when i gave it fuel it would backfire a flame about 6 inches out the exhaust and the header got cherry red. i read about it doin this before but dont remember why it does it. can anyone help me. it quit and then i got it started again and it quit again. i gave up after this. what should i do next.

absente where you at in Virginia Im in Colonial Heights?

ok so i cleaned the needle seat and its working perfectly now. problem is that when i tryed to restart it i flooded it by accident and it wouldnt start. i tryed to remove the plug which by the way wasnt fun. i took off the gas tank and got to the plug and couldnt get it out cuz of the frame bein right over top of the plug hole. does anyone know of a good tool to use. and then i gave up and put every thing back in place. i kicked and kicked and then it fired once and so i drift started it and got it to start. it was running fine and then about a minute later it started sputtering and when i gave it fuel it would backfire a flame about 6 inches out the exhaust and the header got cherry red. i read about it doin this before but dont remember why it does it. can anyone help me. it quit and then i got it started again and it quit again. i gave up after this. what should i do next.

Your post is a little confusing; is it working perfectly now or not?

I presume not.

Could it be that you had some unburned fuel in the exhaust from flooding it, and it ignited; Hence causing the flame?

It kind of sounds like you need to take the carb off and really clean it out good. That is probably where I would start.

BTW, don't worry about the red header, and even asking such a question is considered blasphemous on this board.:worthy:

Your post is a little confusing; is it working perfectly now or not?

I presume not.

Could it be that you had some unburned fuel in the exhaust from flooding it, and it ignited; Hence causing the flame?

It kind of sounds like you need to take the carb off and really clean it out good. That is probably where I would start.

BTW, don't worry about the red header, and even asking such a question is considered blasphemous on this board.:worthy:

well i know the header is suppose to turn red at night but it was very red and was throwing sparks and i know it shouldnt do that but its all fixed now. i think that i didnt let the bowl fill up before i started the bike, after cleanin the carb. it started and ran for a minute and then leaned out because the bowl couldnt fill in time and then it got really hot because of the lean mixture. and then when it didnt have any fuel left it would shut off. this is what i think was happening. so i turned on the fuel and opened the drain on the carb and then turned off fuel. let it drain and then closed the drain and turned the fuel back on. i did this several times to make sure the needle was letting in fuel and closing also. it runs fine now. but i have one more question. if i go down a long straite away thats like 1/2 mile long should it start leaning out if im going wide open. the reason i ask is that i think maybe my main jet is to big and when i am wide open i am emptying the bowl before it can fill back up with fuel. i bought it locally so i dont see why the jet would be to large but i dont know what else it could be.

absente where you at in Virginia Im in Colonial Heights?

lee county, pennington gap. its the southwestern tip of virginia.

ok to begin with the on/off switch is not capable off turning off the fuel but i put a in line fuel switch on the hose from the tank to the carb. im thinkin it cant be the neddle because it doesnt flood out even if its not running but any time the inline fuel switch is on the fuel starts pouring out. i think its coming from the hose that runs out the buttom of the the bowl on the carb. i dont know whats wrong. its the first thumper i have owned but i have had many dirtbikes and atvs so im kinda experienced on carb work. its not just when the bike is leaned over really far either it does it any time the inline switch is on. please help me and thanks ahead of time.

TJ

I know you already put an inline switch in the fuel line, but all you need to do to fix the petcock is replace a $2 rubber gasket inside the petcock. My local dealer who never has anything in stock had about five of them in. They said its a very common failure part.

It takes all of five minutes to swap out and then you can remove the inline fuel switch (which is just one more thing that can fail IMO). Also, when you put the new gasket in make sure to lube the metal parts with some grease.

but i have one more question. if i go down a long straite away thats like 1/2 mile long should it start leaning out if im going wide open. the reason i ask is that i think maybe my main jet is to big and when i am wide open i am emptying the bowl before it can fill back up with fuel. i bought it locally so i dont see why the jet would be to large but i dont know what else it could be.

I no carb expert by any means, however, I can go 'balls to the wall' for a long time (5-10 miles at least) without anything like you described.

I no carb expert by any means, however, I can go 'balls to the wall' for a long time (5-10 miles at least) without anything like you described.

Count me among those that has a hard time believing the MJ could flow at a faster rate than the petcock - assuming normal operation of the system - especially in that short amount of time. A quick back-of-the-envelope calculation that assumes 12,000 rpm works out to about 10 ounces of gas (assuming I didn't seriously screw up the math!) per minute, and a properly functioning petcock should be more than able to supply that.

It would be possible if there is a considerable obstruction in the supply system, so apply some reasoning and begin eliminating possibilities.

:worthy:

Count me among those that has a hard time believing the MJ could flow at a faster rate than the petcock - assuming normal operation of the system - especially in that short amount of time. A quick back-of-the-envelope calculation that assumes 12,000 rpm works out to about 10 ounces of gas (assuming I didn't seriously screw up the math!) per minute, and a properly functioning petcock should be more than able to supply that.

It would be possible if there is a considerable obstruction in the supply system, so apply some reasoning and begin eliminating possibilities.

:worthy:

Absolutely. Also check the gas cap for venting correctly.

ok well i took off for about a half mile and when it started leaning out i loosined the gas cap just a little and then screwed it back on. im pretty sure it cured right up. didnt get to do it several times but im pretty sure its my gas cap. im gona get a new one does anyone recommend one that looks cool and works great.

Take the check valve off and try it. It could be as simple as that.

The check valve is that little plastic piece that is in the vent line about 2 inches above the gas cap.

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