I thought about how to add a throttle lock to my KLR650 for a long time. It is nice to be able to lock the throttle for a few seconds to open a zipper on your jacket, or adjust your mirror. Unfortunately the KLR has a flange on the throttle sleeve that prevents mounting. My purchase of a 9x20 Lathemaster lathe took care of that problem, and I removed the large flange while leaving the smaller inner one that centers the throttle sleeve. The only other mods to the throttle is to drill and tap the lower part of the housing for a bolt to stop the V-C from turning. It is also necessary to trim the grip flange to go under the V-C lock. The grip flange is what locates the V_C, so it needs to hold it towards the throttle housing. Glue the grip back on and you are done. Make sure the throttle is not dragging from the grip and adjust while the glue is still wet.
While I was at it I modded some Kawasaki bar end weights using some of the cheap Bikemaster bar ends. A little lathe work produced these bar ends which will stop a little more of the thump.