If you mean that the bike shifts, you accelerate, then try to shift again and the gear does not change, I usually find that is related to boot to shift lever clearance. Moving the shift lever position can help. Some of my boots shift easier than others based on the toe box height.
Make sure that your boot is not touching the shift lever between shifts. After the lever goes up, and the transmission shifts, the lever has to go all the way back to its resting place (the position where the lever sits when nothing is touching it) before it will be able to shift up again.
The shifting mechanism is basically a ratchet that turns a drum with slots to guide the shift forks. The ratchet has to "reset" back to resting before it will move the drum again. And yes, some gear shifts require more lever travel than others. (e.g. 2-3 may require a longer motion than 5-6)
Hope that helps.
It's more like you go to shift and it's not ready to shift, you have to reshift it again. I've never had to adjust the clutch but I'll check it.
Typo Edit: not 5-6 ... 4-5th!