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Carb issue, cutting out at WFO

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Hey guys I have a 2003 YZ250 that has been sitting for years that I'm trying to fix up and ride. I've been cleaning out the gummed up carb so far so good until I tried to see if fuel flowed into the bowl. I sprayed some carb cleaner into the outside valve thingy and it seems as nothing is flowing into the carb. I've been spraying carb cleaner into it and even compressed air and not seeing it enter the carb bowl.

Any ideas on how I can clean this sucker or am I missing something and the valve seat is just closed. I have my 05 KX250 carb that is looking like a good replacement for tomorrow...

Thanks guys

Edit:

I ended up putting the KX carb on, which upon inspection seems to be identical except for the TPS and PJ connections. I did not connect either connections. I mixed some gas and took her for a spin and while low end and mid is really good its cutting out on the top end. I didnt even check the jetting of the KX carb but I'm thinking it may have to do with the TPS and PJ not hooked up.

Any ideas? I'm going to check the main first as I know the PJ richens the mixtures at high rpms (or lean cant remember haha) so maybe its too rich or just too lean.

Thanks!

Edited by 2strokenut
Hi

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Really the only way is to take the carb off and take it apart,"but not the parts with electrical wires hooked to them".

Remove the float,needle and seat. You should be able to blow carb cleaner thru the fuel line now.

When putting it back togather, the needle has a hook which loops around the float tang.

While in there, unscrew the 2 jets in the center area and the small pilot screw on the lower left outside, then spray every thing clean and clear.

Re-assemble and set the pilot screw at 1 turn out.

Also before hooking the carb back up, make sure fuel flows out of your tank.

Good Luck, Have fun.

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Really the only way is to take the carb off and take it apart,"but not the parts with electrical wires hooked to them".

Remove the float,needle and seat. You should be able to blow carb cleaner thru the fuel line now.

When putting it back togather, the needle has a hook which loops around the float tang.

While in there, unscrew the 2 jets in the center area and the small pilot screw on the lower left outside, then spray every thing clean and clear.

Re-assemble and set the pilot screw at 1 turn out.

Also before hooking the carb back up, make sure fuel flows out of your tank.

Good Luck, Have fun.

I could not blow anything through the main line. The float and seat dont even move. Its like its seized in there.

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Have you taken the carb apart and removed the float/needle assembly?

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Have you taken the carb apart and removed the float/needle assembly?

nope. Didnt come out. Couldn't move it.

I originally had a 160 main and then went to a 165 same thing. Gonna try one more step up then go leaner....

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Couple thoughts...

I have a 2006 YZ250 that sat for 3 years. The biggest problem was the brass pipe/tube thingy that goes from the float bowl area up into the throat of the carb. it is some kind of pressure equalization thing. It has a very tiny hole in it and gets clogged shut very easily by old gas and varnish. My bike would run fine but would break up badly over bumps and jumps.

As for your float and needle being totally stuck, it sounds as if the Viton rubber tip of the needle has glued itself to the seat. you will have to rip it out (literally), clean the seat up well, and put a new needle in there.

As for the KX250 carb... The PJ richens the mixture in the midrange and then closes to lean out the top end for better overrev. The normal (de-energized) state of the PJ solenoid is OPEN. So, if you do not connect power to it, it stays open all the time. That is why you were rich on the top end and are now running such a ridiculously small main jet (152 versus the normal 178). I would be a little scared to run such a small main jet. If I was you, I would plug the PJ circuit and put a more reasonable main jet in.

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Couple thoughts...

I have a 2006 YZ250 that sat for 3 years. The biggest problem was the brass pipe/tube thingy that goes from the float bowl area up into the throat of the carb. it is some kind of pressure equalization thing. It has a very tiny hole in it and gets clogged shut very easily by old gas and varnish. My bike would run fine but would break up badly over bumps and jumps.

As for your float and needle being totally stuck, it sounds as if the Viton rubber tip of the needle has glued itself to the seat. you will have to rip it out (literally), clean the seat up well, and put a new needle in there.

As for the KX250 carb... The PJ richens the mixture in the midrange and then closes to lean out the top end for better overrev. The normal (de-energized) state of the PJ solenoid is OPEN. So, if you do not connect power to it, it stays open all the time. That is why you were rich on the top end and are now running such a ridiculously small main jet (152 versus the normal 178). I would be a little scared to run such a small main jet. If I was you, I would plug the PJ circuit and put a more reasonable main jet in.

That's exactly the problem, that brass thing. Do you know which hole it is?

Thanks for the info! I think I could go leaner but 152 is the lowest I have. I would connect the PJ but the KX has both circuits in one connector while the YZ has 2 separate connections

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Right, I understand the different connectors. Just close off the PJ passage where the fuel flows. If you take the float bowl off you will see where the actual small jet is that supplies the fuel up to the solenoid and the brass nozzle in the throat of the carb. You can probably remove this small jet and put a BB or something in there to close it off. Then you can put a bigger main jet in.

The brass thing I am talking about is is in front of the pilot jet and main jet. It's like a tall, skinny cylindrical pipe. It has a very tiny hole init and gets clogged really easy. And it is pressed in so you can't replace it.

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Right, I understand the different connectors. Just close off the PJ passage where the fuel flows. If you take the float bowl off you will see where the actual small jet is that supplies the fuel up to the solenoid and the brass nozzle in the throat of the carb. You can probably remove this small jet and put a BB or something in there to close it off. Then you can put a bigger main jet in.

The brass thing I am talking about is is in front of the pilot jet and main jet. It's like a tall, skinny cylindrical pipe. It has a very tiny hole init and gets clogged really easy. And it is pressed in so you can't replace it.

Ohhhhhhhhh I see now, the brass thing you are talking about is fine, no blockage I was talking about outside fuel line input. So plugging that jet off with a BlackBerry will make it be in the closed position and NOT spray more fuel allowing me to run a 160 or higher like normal?

But seriously, what can I block it with? lol

Thanks for the help man

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Ohhhhhhhhh I see now, the brass thing you are talking about is fine, no blockage I was talking about outside fuel line input. So plugging that jet off with a BlackBerry will make it be in the closed position and NOT spray more fuel allowing me to run a 160 or higher like normal?

But seriously, what can I block it with? lol

Thanks for the help man

You can plug it with whatever you can find. I'd probably clean it up real good, let it sit for several hours to de-vaporize and fill it with solder.

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You can plug it with whatever you can find. I'd probably clean it up real good, let it sit for several hours to de-vaporize and fill it with solder.

Thanks guys, I took it out today and top end suffered but ran decently. Unfortunately I need to put the carb back on my KX so I need to figure out how to clean the YZ carb.

If fuel is not flowing in from the outside brass thing does that mean my needle and seat are gummed up?

Thanks guys

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Thats a great explanation! Thanks Hallsy.

Do you guys recommend getting a Carb Rebuild kit like this one?

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=370548892782&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en#ht_2415wt_939

I'm thinking of keeping this YZ and getting rid of my KX250 since it should command a premium coming into the riding season and I'm broke.

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Ok I'm not seeing what some are seeing. Help me out.

Red and Green Arrow- There is a cylinder and then an object inside the cylinder that green points to. Is the the float valve that should move? It does not budge. I'm not seeing where I would plug up the PJ inlet. (this is the YZ carb BTW)

Yellow is just what I'm talking about where no fuel goes through.

thanks fellas

YZ250Carb.jpg

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Fuel flows in at the yellow arrow. It then flows into the bowl through the area with the green and red arrow.

The thing the red arrow is pointing to is the inlet needle. If it does not fall out on it's own, it's stuck in place. Pull it out carefully. There is a brass seat pressed into the carb body underneath this needle. It is not replaceable, so clean it as best as you can.

With the inlet needle out, pour some gas into the tube with the yellow arrow. You will see if flows through the opening where the green arrow is.

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Fuel flows in at the yellow arrow. It then flows into the bowl through the area with the green and red arrow.

The thing the red arrow is pointing to is the inlet needle. If it does not fall out on it's own, it's stuck in place. Pull it out carefully. There is a brass seat pressed into the carb body underneath this needle. It is not replaceable, so clean it as best as you can.

With the inlet needle out, pour some gas into the tube with the yellow arrow. You will see if flows through the opening where the green arrow is.

Thanks GMO, just to be clear so I don't eff this thing up, the brass cylinder pressed into that area houses the inlet needle which the green arrow is pointing to, and that should come out but not the brass cylinder... correct?

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Thanks GMO, just to be clear so I don't eff this thing up, the brass cylinder pressed into that area houses the inlet needle which the green arrow is pointing to, and that should come out but not the brass cylinder... correct?

👍

You have it!

Let me redo my post earlier, I got red and green backwards

Fuel flows in at the yellow arrow. It then flows into the bowl through the area with the green and red arrow.

The thing the green arrow is pointing to is the inlet needle. If it does not fall out on it's own, it's stuck in place. Pull it out carefully. There is a brass seat pressed into the carb body underneath this needle red. It is not replaceable, so clean it as best as you can.

With the inlet needle out, pour some gas into the tube with the yellow arrow. You will see if flows through the opening where the green arrow is.

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👍

You have it!

Alright! Well, now I have figure out what to use to pry it out. Now, once it does come out I assume there is a rubber gasket in there that needs to be replaced, correct? I wish there was some sort of diagram that showed it a little better than the OEM parts section on Motosportoutlet. Thanks again

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As I said in my earlier post, the inlet needle (green arrow) has a Viton rubber tip on it. That rubber tip is basically bonded to the brass seat (it's not supposed to be, yours is just stuck from sitting and rotting). You will basically have to rip it out of there destroying the rubber tip in the process. You will then have to clean up the brass seat getting the chunks of rubber out and put a new needle in.

I think your bigger problem is going to be that brass tube thingy I was talking about, on the right side of your photo. See it is all corroded green like the statue of liberty? The tiny hole in that thing is probably totally clogged shut with corrosion. I'd be amazed if it isn't.

That carb is corroded very badly. Way worse than mine was and I had to get a new carb. All the cleaning in the world couldn't fix mine.

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