This is what should be in the handlebar:
1, bar end weight, held in with a short Allen bolt. To remove this hold the weight and undo the Allen bolt (I had to wrap a bit of leather round the weight & hold it with a pipe wrench).
2, this reveals the end of the counter weight, with an O ring & a roll pin to remove.
3, next is the retaining bolt (24mm spanner, M18 thread).
4, now the counter weight can be pulled out, which has a short rubber tube to stop the whole assembly from working it's way out of the handlebar.
If it won't come out, you can get a 5mm drill between the counter weight rod & the handlebar tube to remove whatever is jammed up there.