Raif,
The spring loaded bit that the wire goes into is the holder for the speedo bulb. If you undo the knurled ring, the holder complete with the bulb can be withdrawn. To attempt any other work on the speedo, you will need to remove the rim and glass - then remove the 2 cheesehead screws from the underside of the speedo head ( if your speedo has a trip mileage, you will also have to remove the trip knob). Having done this, the works can be withdrawn from the case (it may be a bit stubborn as the paper gasket sometimes sticks it to the case). With the works removed, you will probably be horrified at it's complexity, but don't be put off. The whole mechanism is akin to a clock (with a balance wheel and all sorts of levers). Most problems with chronometrics that have been idle for some time can be attributed to the oil/grease having dried up or become very sticky. A spray of WD40 and a careful clean out usually results in the unit working again. A chronometric speedo is totally mechanical and either works or it doesn't - it will not give a false reading (either high or low), unlike later magnetic units that can be affected by the distance between the magnet and the reacting disc, or the drag on the needle.
Hope this is of some help,
Regards,
Eddie.
