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2003 450exc Carb HELP!!

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Ok so I have this problem where the drain plug on the carb (bottom of the carb with a hose coming out of it and one bolt) keeps leaking after I run my bike. It leaks both when its running and when its off but only after the bike has been running. It is constant drips. Would this be the float sticking and overflowing? I am starting to just think that the drain plug bolt is not closing all the way down but I tightened it pretty good. I was planning on just pulling the carb today but realized its not just an hour job to pull it and would like to know if I can just pull the bottom. Thank you for your help everyone

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If it only happens after riding a little while.

My guess is the check ball in the cap is sticking causing the gas tank to built pressure (from heat ) and this will sink the float and flood the carb. The gas will come out of the over flow tube. (Not the drain tube. If it comes out the bowl drain tube, someting is wrong with the shut off valve in the bowl.)

Remove the check ball in the cap or remove any of those check valves that people add to the cap vent line. The tank must vent in both directions.

Very common problem.

If it happens any time the petcock is on (cold or hot) , then mostly it is the O-ring that is on the O.D. of the seat (needle/seat) has failed. Replace the O-ring.

Another very common problem.

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Yes in those years the rubber parts where not all compatable with the modern gas, abt 2001 they changed rubber suppliers on most pieces but they must have had a big bin of old rubber for the Oring where the seat presses into the carb body, I fix a couple a week

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I just had the same thing on my 03 exc 450. It is your oring. Order one from Travis at http://www.thumperstore.com/

Tell them you need the float needle oring for your bike and they will ship it to ya. It will be 6 dollars. If the gal on the phone is confused, ask for travis. It is a really simple fix. You don't have to pull the carb to do it, but you should pull it and give the whole thing a good cleaning. The float needle is held in with a philips head screw. Just pull the screw, pull the float needle out, replace the oring, and put it all back together. If you have recently cleaned the carb, just loosen the boots, spin the carb to the side, pull the bowl and you can access the float needle really easy. The new orings are made of viton and will not deteriorate. When you pull out the old one, it will be all smashed and brittle. Don't even mess with just cleaning or doing the tank breather trick (do that too, in addition to the oring). I messed with every fix and mine still leaked till I replaced the oring.

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Thanks,

We're looking at carb cleaning issues for an '01 due to chronic misery for cold starting. It used to start fine, and has been getting worse with time. We plan to clean and check the carb before changing the jetting. I'll add this to the list. I think my friend has already updated the needle and seat. Regardless the carb and fuel system will be checked.

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Hey! I realize this post is from months ago, but I just wanna say thank you to L-Vie and Wakewop for their wisdom on this subject, I was experiencing the exact same problem on my 02 520 EXC and sure enough, that damn o-ring was as hard as a rock and doing a terrible job of sealing. The whole process took me maybe an hour with the, tilt the carb in the boot, method and it runs like a raped ape now! Thanks again guys!!!

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I know its an old thread but I had the same oring go out on me again and now the thumperstore doesn't carry it anymore. Does anyone know where I can get this oring without having to buy the whole needle kit. Thank you

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I just got one from Travis. Email him at travis@tumperracing.net

When I pulled my float seat out, it looked like this. I think I'm in for more than a simple o-ring replacement. I have to clean the whole thing now.

IMAG0026.jpg

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