I have a few thousand miles on the bike and I recently had to take up some slack on the clutch cable, which I did, but now, I can only shift into the first 3 gears. I can't go from 3rd to 4th, etc. Can you adjust the clutch cable too much?
When you are moving, you don't even need the clutch to shift up or down. If the bike is not shifting, there is a good chance it's something else, most likely the angle of the shift arm on the transmission or at the shifter. Make sure both arms are pointing 12 oclock and the hiems are lubed and moving free.