Lost 4th gear in 2004 Honda Recon 250

I was riding this afternoon and went to shift into 4th gear and heard a popping noise. I released the gas when I heard this and when I went to hit the gas again it wouldn’t go anywhere. I shifted through the rest of my gears, R, 1-3, and 5 and everything ran fine (except a hard shift into 5th, not toooo hard but definitely noticeable).

A few problems you can rule of the list because I’ve already checked:

- I just replaced the oil last week (10w-40 valvoline atv oil) and it is at the top of the fill line
- I have tightened the clutch adjustment

Any recommendations or suggestions on what the problem could be would be greatly appreciated.

Thanks in advance.

TM