Hi CJ. Your speedo is a mechanical device that does not stop working with non-use. The problem will be in one of three areas. The head itself, the cable. the drive in the transmission. Start by removing the cable and housing from the back of the head. Pull it down so you can see the cable inside. The cable should stick out about 1" and be square, not round. Grab the end of the cable with your hand or pliers and try to turn in either direction. If it turns continuously, you have either a broken cable or it is not engaged to the drive in the trans. If it will rotate in either direction more than 1/4 turn, then you have a bad cable that will cause the needle to bounce in operation. A good cable will turn less than 1/4 turn. If cable and drive seem OK, take a squared end piece of cable and insert it into the back of the speedo and spin it in both directions. The needle will bounce. If it won't, you have found a problem. Speedo's can be dissassembled and freed up. Hope this gets you started.