It should not be necessary to remove the right hand grip from the throttle tube to perform the service. A sticky throttle could be attributed to either debris between the bar and throttle tube or a sticky bowden cable.
The 92 K100 appears to have the 20mm master according to RealOEM. To remove the right hand grip, disconnect the heated grip connection under the tank on the left side. This allows enough slack to pull through the handlebar. Disconnect the bowden cable from the MC. On the MC, you'll notice a plate with two Philips screws secures the throttle tube to the MC. Remove the two screws. It will be necessary to pull back on the grip rubber because it partially conceals the screw and prevents removal. Once the two screws are remove the grip and throttle come off the handlebar; gently pull the grip off the bar, feeding the heater wire to prevent binding. Once the tube is clear of the end of the bar, you can service it by cleaning the inside of the tube and outside of the exposed bar. Assembly is reverse of disassembly. Before reattaching the bowden cable test the throttle for free movement and correct any remaining stickiness. While the bowden cable is disconnected from the MC, test it for free movement.
If you still have stickiness after reassembly, routing of the bowden cable could be the cause.
The K75 looks to have the old 13mm MC. Stickiness could be old grease in the gear mechanism, debris between the handle bar and throttle tube or a sticky bowden cable.
Open the cover over the gear mechanism in the MC and make sure the gearing is clean and well adjusted. This is described in the service manual. Lightly grease.
The throttle tube doesn't easily come away from the MC, so best remedy to clean the bar is to remove the MC as a unit. This requires the heater cable to be disconnected as above. The MC gets loosened from the handlebar and the easiest is to remove the handle bar from the triple tree. That provides slack in the brake lines. It should be possible to pull the MC off the bar but it's going to require fiddling with the bar, feeding heater cable and wiggling off the MC, while trying to find slack in the brake line. Once free, clean the handle bar and use a test tube brush to clean the throttle tube. The wire will be in the way so work carefully around it and avoid using harsh cleaners.
Same advice goes for the bowden cable routing if stickiness remains after reassembly.
