400ex wont run without choke

[blacktrx400ex]

I bought a brand new 2007 honda 400ex recently. I have ridden it about 4 times. The first three times it ran perfect. The next time it didnt. It wont idle without the choke being on even after being warmed up and it wont run properly unless the choke is fully on. If I put it at half choke then it runs and idles fine at half throttle but if I go full throttle it bogs down and almost dies. It ran fine one day then the next this happened. I have no idea what it could be.

[rooster300ex]

main jet could of fell out. Just a guess. Then again my buddies 400ex would idle just fine when that happend. I would clean the carb and airfilter really good. Being new I don't see this being the problem but give it a shot

[jstalnaker]

did you was it and get the filter wet?
is your gas tank vent hose plugged?

[440exhondaman99]

i would try cleaning the carb... mine did the same thing... while you got the carb apart go with a 42 pilot jet... it will help so much on starting wont ever need the choke... if you have a slip on you need to atleast go with a 155 main jet to or you will burn your vavle seals up because they come stock running lean out of the factory... but clean the carb and air filter im guesing thats your problem

[350ex]

It shouldnt be dirty, you said it was brand new, right? The first thing that came to mind was something is clogged in the card, but that shouldnt be the case. Take it back to the dealer have them fix it. Should be under warranty if its new.

[fearlessfred]

dont know the carb u are working on but i have had the clip on the needle come off and cause the same condition on my old 250rs just an idea

[tato1019]

hey 440exhonda man u said something about the valve seals burnin up if u dnt jet it with an aftermarket exhaust. wel i removed the silencer on the stock exhaust would that effect my engine?

[440exhondaman99]

if you put a aftermarket slip on exhuast and dont jet it to atleast a 155 main jet then after a while it will burn your exhaust side valve seals up... i did it to mine... the seals are cheap its just the part of doing it cuz its a pain.. but bump your main jet up to a 155 or 160 even for a lil more power and to be safe on your vavle seals... they start so much easier to if you put a 42 pilot jet in also.... i would clean the carb you said its an 07 so theres a chance the gas has had been sittin in it and gummed up your carb....