How do you lubricate the shifter on a Suzuki c50?

It's a satisfyingly easy, five-minute job.

Use a 14mm wrench to remove the locknut on the backside of the shift lever; you'll see it at the mid-point, where the lever pivots. Or, use the same wrench to loosen the chrome bolt from the front. I used two 14mm open wrenches: one to hold the bolt, the other to turn the locknut.

When you remove the bolt and locknut, you'll find a cylindrical bushing; it inserts on the back side of the shifter. Smear the inside with grease, and reassemble. That's it.