Is speedo and all related lights and everything dead? Or just the speedo needle? What happens when you turn ignition on? If it is only needle, do what LoneEagle suggested, pull speed sensor on top of tranny, has two bolts and is oval shaped, pull out and look for any crap or shavings on the sensor, clean re-install and recheck.
2000 Road King on Mulholland approaching the Rock Store. BEFORE and After at 7000' elevation in Central Ca USFS Scenic Byway