Hoping this isn’t a dumb question, but just not sure. I want to replace my damaged speedometer with a nicer one. The nicer one has about 3k more miles than my bike has on it. Do I chuck the cable end in a drill and run it backwards?  Any easier way to do this? Assuming it will take quite a while?
Thanks!

Not sure how it's done, probably from inside but Deet restored mine and reset it to zero per my request, the DMV don't care about millage on these old bikes so it's perfectly legal.

Yeah, I started thinking maybe this was too “sketchy “ a question for anyone to answer. In MN, DOT doesn’t even require mileage to register/title vintage bikes, can’t remember the year cutoff, but I know mine qualifies. I have no way of knowing if mine is actual mileage (under 1800), but no reason to really doubt it either.
 I thought about asking Deet to look at mine, but I can’t imagine a way to straighten the upper rim(under the rubber cover). It got thumped pretty hard by something… I guess make it round again is actually what I need…
 

Three possible ways to maybe get the result you're after:-

1) Wind back with a drill and cable as you suggest. I don't know what, if any, effect this might have on the separate mileometer.
2) Open up the replacement speedo and wind back by hand.
3) Open up the existing and replacement speedos and swap the mechanisms over.

For both 2 and 3, DEET will do a top job for you, although there will obviously be an exchange of beer tokens involved!

Hey Gr8 unc, thanks for the reply! I hadn’t thought of #3, and kind of like that one the best!
To get inside, one has to roll back the top edge, correct? Not sure I’m up for that… Can’t say I’ve looked at it yet, but sounds like something I’d be good at mucking up…

Also, if I were to turn it back that much, does it hurt the actual mechanism that shows the speed? IE, what the needle is attached to?

Not sure of that, but I guess there is potential for it.

Getting the lip up and the mechanism out is relatively straightforward - the skill is "re-sealing" the lip to make it look like no-one has been in there. 

Gotta open it up.

cliff

Yes, I can see where that would be the “trick”… Thanks!

You can use a drill to run it backwards, but it will take a long time. Best to set it up in some kind of jig and then lock the drill ON.
Opening it up to change the odometer is the fastest way to do it, but it isn't easy and unless you know what you are doing...