01 honda 400ex... whats wrong?

[honda450r! dude]

my 01 400ex is causing problems! I start it up and it runs fine for a while and than it starts cutting out when you rev it up and eventually it dies and wont start again..... Is it the carburater? Please help...

[on the rocks]

ever adjust the valves? sounds like it warming up has something to do with it. maybe the cylinder is worn and loses compression as it expands.

only thing i could think of in the carb causing it would be the floats not allowing enough gas in the bole quick enough.

how long does it have to sit to start back up? if its just a few min ( that would be enough time for the gas to trickle in to the bole) i bet its the floats or a clogged needle and seat. if its like half an hour or longer i bed its motor due to the longer time for it to coll and all the motor components to go back to the size they are cool.

[honda450r! dude]

I took the carb apart and everything seems to be alright..... except theres a little plastic piece at the end of a hose that broke in half and inside it has a little needle and a spring......Ill post pics of it... I dont know what this is or if it has anything to do with it.

[honda450r! dude]

heres another pic of the plate and needle...

[Stickman400]

That could be your problem, it's hard to tell though. It's number 28 in this: http://www.motosport.com/atv/oem-parts/HONDA/2001/TRX400EX/CARBURETOR It says it's an air cut off valve. Replace it and see what happens.