The bobbincase sets inside of the hook that spins around it,put some oil in the groove that the bobbincase sets in.Also if your clutch feels like it doesn't take much to trip it you can adjust it by turning the screw w/a arrow on it on the clutch it's the larger screw on the end of the longer piece that looks like a chicken bone.
The screw I'm talking about is @ the end of the screwdriver in this pic,it's really not a screw because it doesn't have any threads on it & has a set screw that holds it tight on the belt side of the belt pulley,you should be able to spin it if needed,the clutch in the pic is set @ the max tightness when the arrow is pointing towards the belt.