I'm at a stop light in first gear.
The light changes.
I take off in first gear.
I pull the clutch, I pull the gear lever up as much as I can with my foot and the bike won't shift into second.
I twist on the throttle and realize I'm in neutral.

This happened before, every once in a while so I ignored it.

The last time I rode, it happened a lot.

Everything else works fine.

I shift all the way down (from 5th gear to first gear) very easily with no problems.

I can also shift up (from 2nd gear to 5th gear) just as easily.


The issue is shifting from 1st gear into 2nd gear.

What could be the problem? What should I check or adjust to elevate the problem?