Why are my gears sticking on my motorcycle?

One common reason for the gears sticking is incorect oil type, motorcycles have wet clutch and specific motorcycle oil must be used, otherwise the clutch drags and gears are hard to shift.Aside from any major problems with the transmission itself, is your clutch working properly? Is it set correctly and fully disengaged when it is not being used. I would start here. You may need new plates in your clutch itself.