I've looked through a heap of other topics and couldn't find exactly what I was looking for.

I've got an '07 KX450f. I was riding the other day and it was changing gears fine (2nd - 5th), but every time I went to shift from neutral to first to take off it wouldn't shift into first unless I pushed the shifter down really hard. Now it's stuck in neutral and selects 1st occasionally if I play around with it for a while. My first thought was a broken selector because i've had that happen before, but i pulled the clutch and clutch basket off and the shifter doesn't appear to be damaged at all. Everything else appears to be in order, that being said I have limited knowledge of the inner workings of a bike so I could be missing something. Does anyone have any thoughts as to what it could be? Want to explore all avenue's before I split the case (don't want to do that if I don't have to, but I get the feeling I may have to). Any help would be appreciated, cheers.

**Edit: Also, when I was undoing the nut that holds the clutch basket on I was able to shift fine from 1st - 5th in order to put my foot on the back brake and undo the nut without the clutch basket spinning (because I didn't have the clutch holder tool) but it has since decided to stay in neutral

 

Since I am not familiar with your trans, I checked out the fiche. Looks like a case split after looking at that. However, I am unsure on your issue at hand.
Welcome to KF and good luck