Fixing notchy throttle action

There are a number of reasons for a "notchy" or "grabby" twist throttle:

1. Kinked, pinched, unlubricated, or old cables.
2. Carb pistons scuffing in their bores.
3. Hand grip rubbing on something such as a bar end mirror.
4. Worn hand grip throttle gears. 

Let's talk about worn gears.  If you have bar end mirrors or lights, remove them.  Unscrew the gear box flat head screw and open the gear box lid. Pull the grip off the handlebar and examine the gears. 

Worn gears look something like this:  

Note how the metal is "folded" over the edge of the tooth.

The wear pattern is clearly visible.

You can get a bit more life out of the gears by filing off the lips and smoothing out the face of the teeth to reduce the wear spots.

Like this.

Reassemble with a dab of grease and hopefully that removed some of the notchiness.