I cant remember the name of it but inside the speedometer, there is a little metal pice that looks like a toothpick. That is what reads how fast you are going, check it out, that could be broken or not even there. check it out.
Check the gear at the end of the cable. When you pull it off you will be able to tell if everything is kosher in there. Also make sure the cable is free to spin. I always grease the inside of that cover before i put it back on.
sounds like you broke the coupler that goes into the drive shaft behind the spedo pickup under the secondary, most likely that bearing on the shaft has locked up and needs to be replaced. that has been our finding.
mine is bad right now too. key going to driveshaft from the speedo gear was twisted in half. The problem was not the main shaft bearing though, it's the actual speedo gear/housing itself. It is locked up for some reason. I see that part is about $60. Anyone have any luck getting these to work again after theyve locked up?