Not sure about the GS, but on most R bikes you simply remove the large Phillips Head Screw, as if you were going to replace a throttle cable. That releases the twist grip tube and exposes the gears.

I have experience with airheads, done a lot of work on the older models. This Type C set-up, however, is my first. Casually looking at it from the rider's seat, the throttle gear mechanism cover and it's single hold-down screw appeared encumbered by the master cylinder reservoir sitting on top.

This afternoon, I had a closer look and now see the seam that defines a separate cover over the cogs. Once I get to that slotted screw, I assume that small cap will come off and reveal the guts.

I still am not yet sure how the cable pulls are attached inside since that reservoir covers up the area that I would expect to find all of that.

This is basic stuff, though. I'll try to post some pics when I get things apart. May help someone in the future.

Pic made today-

Yes, remove that single big strew.

The cable ends attaches to a block that is pulled to the right by a chain that wraps around a capstan. The large screw is at the center of the capstan. The capstan and twist grip tube have a mating set of bevel gears.

• Be sure and note the relative position of the twist grip tube before pulling it off the handle bar. The same boss that retains the tube in the twist grip assembly also limits the twist grip rotation so that the rider doesn't pull on the small chain too hard. If you replace the tube in the wrong position, then you may only get a partial throttle opening.

You'll want to grease the inside of the twist grip tube, the bevel gears, the chain and the capstan center pivot.