but now when i go to put into 1st gear she jumps forward
as if clutch is not fully engaging
have you any ideas what might of happened
Sounds more like the clutch isn't fully
disengaging.
Have you had the countershaft cover off? If so, it may be possible you didn't get the clutch slave lined back up right (seems like a stretch though).
Or your clutch may need to be bled, or maybe it's not holding pressure/leaking.
If it jumps a little, but doesn't go anywhere, that's pretty normal, my bike has always done that.