leaking carb

Hello, I'm new to the site and have been looking at anything and everything to remedy my problem with my 1998 wr400f. I just got the bike and it seems to be in pretty good condition. Bike started right up with in first couple kicks and runs real strong. Took the bike out the other day and took a little spill in a corner. Now the carb constantly leaks fuel from the over flow hose at the bottom of the bowl like the float is stuck. I removed the carb looked took the bowl off and inspected the lower half of the carb. All seems fine but when i put it back on the bike fuel just flows out until the tank is empty. the bike floods and wont start. any help would be appreciated. I will be looking to pick up a repair manual as soon as i can to remedy this and any other problems that I may have but im stumped with this one.

thanks for any help.


Your float valve is probably stuck open with some debris. Take the carb apart again. Clean and clear the float valve area of the debris. Inspect the needle valve for any markings that would prevent proper seal of the fuel. If needle valve is bad, replace it.

A TEMPORARILY work around is to turn your petcock to the off position when not in use to prevent fuel to flow into the carb until you replace the needle valve or remove the debris.

Even more likely is the oring between the seat and carb body has cracked. Cost is just a few dollars for a new one.

Thanks for the input. I removed the float bowl again and found lots of debri on the fuel inlet screen and the o-ring is hard and smashed flat. Looks like im going to be buying those parts and trying again. Wish me luck.

installed the new needle and and seat. doesnt seem to be leaking fuel anymore but still cant get the bike to start. I'm looking for one two or three different but specific starting sequences that i can try? I need to figure out what will work for this bike and me but after hours of sifting through the net my brain hurts and I still dont have a running machine. any help and or links to help would be appreciated.

the FAQ has a couple videos on how to start your thumper.

The manual I posted the link to also has a section in it about starting procedures.

If the bike hasn't started since you flooded it and you've been kicking it a lot it's probably really flooded now. I've flooded my 426 so badly I had to take the header pipe off and drain the fuel out of it.

I suggest holding your de-comp lever in and kicking it over 15-20 times to clear the cylinder. Then use the standard starting technique without choke or any throttle. With any luck it'll pop on the first couple kicks (or it may actually start). After it's popped (if it hasn't started) hold the throttle just off idle (I'm talking lifting the slide in the carb half a millimetre, if that. If you can't hold the throttle steady while kicking wind the idle nob on the carb in a bit) and kick it again, it should start. If it doesn't you may have to clear the cylinder again or take the header off and drain it (I'm not kidding, I did have to do this).

Good luck.

PS: If you're bike has an auto-decomp cam and the de-comp lever removed (as mine does) you have to pull the spark plug and kick it over to clear the cylinder.

Thank You Alternative!!!!!! After getting my stitches last night after the kick start jabbed a hole in my leg. I came home today. kicked the bike over witht he decomp lever pulled 25 times. followed your starting advise and low and behold it started on the first kick!!!! Thank you fro your help and advise. I feel so much better now that the bike starts and i have a better idea of what it takes to make it a great bike to own.

Always happy to help :busted:. Glad to here you got it running, it should start 1-2 kicks now (hot or cold, remember when cold pull the choke and don't touch the throttle) if it's jetted right and you're using the right technique.

ok... well i was just on the phone with drgnfox as i tried to get my 2001 426 to start... i did the same thing almost verbatem (besides the corner spill) as he did.

got a 426, seems to be in great shape, started on the 3rd or 4th kick everytime, got it out the first time opened it up alittle (got into 4th gear), when slowing for a turn i pulled in the clutch to coast the turn slowly as i was on gravel and the engine died. that was last saturday and i have yet to get it started.

i have pulled the carb, taken it completely apart and cleaned each piece by the book (manual), replaced the spark plug, tried the starting procedure in the manual, no go. i then talked with drgnfox and heard his success so tonight i cleaned the plug, replaced the oil, 'deflooded' it and when i tried the procedure he was suggested... no luck. there is some fuel leaking out of the breathers, I'm just not sure what is going on. i did have to change the throttle cable, but its set up just like the old one, so im not sure that matters

at this point i will take any and all suggestions.

thanks for listening,


ps - it has a Pro-Circuit Type-496 pipe on it, and it has been rejetted

William1 nailed it. After a few years the O-ring that seals the brass needle seat fitting to the carb body, will dry out and start bypassing fuel along the outside of the needle seat, into the float bowl. The float needle can not stop this flow. Change the needle seat o-ring and make sure the float is set right. WR Dave.

well, i got it started... just needed to find what she needed... whoever said 426s were like women had it right. i found what she liked and now she starts up every time, not first kick everytime, but within 3 to 5 kicks... that works for me!

Just make sure to learn the start procedure and stay away from the throttle while starting. For what it's worth, I really like the better handling and e-start on my '07 450, but in some situations I miss my perfectly jetted, unstoppable WR426. WR Dave

Where can you get just the needle seat o-ring? It looks like the seat and valve are only available as a set.

In my experiance you cant just get the o ring. I found that very irritating since the set was $60 plus. what a rip of yamaha.

The O-Ring doesn't have to come from Yamaha, any auto parts store can get you an o-ring ( $1) , just as long as it is compatible with gasoline. WR Dave

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