I just changed the oil in my 250x and it wont start now what could i've done wrong.

 

This is the old 250X, not the newer 250EX...????

Nothing you do during an oil change, should effect starting in any way. Will it turn over, but just won't catch? Or, is it just completely dead???

Did you happen to bump the kill switch???

 

its the old 250x

it starts to turn over then it dies.

when i pull in the throttle is also dies

 

did u check the usual things like gas, try putting on reserve, or the kill switch like recon said?