I saw a post a coupla weeks back about a fellow who inserted something into the trip odo reset knob on his vintage 2-stroke and made it work. This got me to thinkin' ...
All-original 1978 TS185, the knob to pull out and reset the trip odometer no longer functions, it just pulls off completely. I found a miscellaneous "small screw" to stick in there but it didn't go. I pulled off the knob and the rubber seal to expose the trip odo reset shaft. Sure 'nuff, when I reach in with needle-nose pliers, I can pull that shaft out, it goes "click" and then it can wind/rewind the trip odo. Cool, it functions, I just need to get the knob attached to the shaft somehow.
I took a closer look at the shaft: metallic, with what appears to be very small/very fine threads in the middle. Off the speedo comes and I take it to my local Ace Hardware store. The HHM mates it up with a very small 2mm x 8mm screw that threads very nicely into said threaded hole.
Issue FIXED, for a wholloping $0.45. 2mm x 8mm screw. There you have it.
I no longer have to rely upon a Sharpie and pieces of duct or masking tape stuck to the fuel tank to remind me of how long it's been since I filled up the tank. Tape/Sharpie is now reserved for directions (analong/old school version of GPS).