Personally i havent done it, but the principle is fairly basic...
Yes it is a copper core, but you might want to source a small temp-sensor from either a bike or car and adapt (solder in) the section you need to screw the sensor in (all sensors fail at some stage, so it would be wise to make it removable).
Would probably cost you $20 to get a section soldered by a pro...
Then hook up your guage on the bike and connect away..
An LED bar guage would look pretty cool, and i think jaycar has it in kit form
just a few thoughts...
