400ex rev problem

[rubicon500kid]

ok so i was riding my 400ex and it was runing good then it started to feal like it was reving to fast like half throtel it was hiting the rev limiter  and then when i was in 5th if i mashed it it would rev up then go
what could be wrong with it
i think its the
clutch
or the rev box has water in it

[Toomey]

I'd check to see if your air filter fell off, making it run lean.  Was it backfiring when you let off the gas at all?

[kfx400rob]

when i had dirt in my main jet it felt just like it was the rev limiter so it could be that unless its reving realy high then mayb the clutch is slipping. but idk realy

[Jax_Rdr_01]

this might sound stupid but was the choke on because i know on my ex when i had the choke on it hit the rev limit at half throttle and reved up very fast.

[rubicon500kid]

no it wasnt the choke was off