400ex cutting out at mid to hiqh rpm

[oldred400]

Well for starters im new to this forum, but for the record i did not just join because of this problem, i actually joined before this happened i just hadn't been able to post. So as for the problem, i have an '04 400ex, i bought it about a month ago, ive taken it riding a few times and it runs great. this weekend i took it out and let a friend ride it and he went bombing off a dune and pretty much face planted it into the sand. Among other more obvious injuries to the quad (and to the rider, dont worry hes just a little sore), it now isnt running right. it runs perfect at low rpms but as soon as you get up to mid to high rpms it pops and sputters and completely falls on its face, almost as if it had hit a limiter way to early. Ive checked all the electrical connections, everything seems fine, im wondering if something in the carb got jammed or stuck? It came with a yoshimura slip on, K&N air filter and the guy said its re-jetted but he didnt know what size jets since it was like that when he bought it. anybody got any ideas? thanks in advance for any help, this seems like a good forum, im looking forward to being here.

[mattonln]

im thinkin your main jet fell out or got clogged probably. pull the big nut off the bottom of the carb and the main jet is right there.

[oldred400]

i found the problem, i decided to take the carb off and clean everything out, but when i went to unbolt it i found the main intake hose from the air filter had come undone. i put it back on and took it for a spin and its runnin like a champ. it must have just been letting in too much air and couldnt put out enough fuel to compensate. so pretty much the same effect as if the main jet was clogged.