vapor (or similar) speedo

I've searched the forum and found threads dealing with some of the technical aspects of wiring these up, but what I'm wondering is what issues arise when fitting one to a bike used on the road. Specifically I'm talking about the mileage of the bike... if you come to sell it, it has to display the correct mileage right? So, do you have to get the new display certified as being fitted at a certain mileage or something? (also wondered about this when people fit new engines etc etc). Sorry if this is a naiive question!

The reason I'm asking is that I want to swap out the headlight of the sv for something different, but the standard display looks bulky and out of place without the standard plastic (this is a k5 naked im on about). I don't want to just cover it with a buell fly screen or something as its been done too many times already!

Doesn't have to display the correct milage. You just can't lie about it, otherwise swapping clocks in itself would be illegal. If you say "it has 3,000 miles" but in actual fact the old clocks are showing 18,500, then that's illegal.

get documented proof of mileage and be honest and it'll be ok

Take a photo of your clocks and something with todays date on it, then do the same with the vapor once you've set the mileage on it.

Your MOT may have the mileage on it which would be an indication to a buyer. Keeping the old clocks and providing them when you sell could be another option.

Right great. Not that I'm going to be doing this for a while yet! When I do I'll no doubt be back for help when I do something wrong :P