certainly, they're usually full of crud after 50 years, but if the needle goes to 80 when you're actually doing 50, the dirt would just be causing the slowness, some damage is making it inaccurate, the mechanism can't spin faster than the cable tells it to, so it's the reading that's the real problem - when you replaced the needle is the most likely cause, did you get the needle on correctly? any struggle there? have you checked the tech tip about the AD speedo? the mechanism is delicate, there's a fine coil spring that "fights" the movement caused by the spinning magnet, keeping the needle moving steady and balancing the magnets torque when it gets to the right speed, the spring is critical to accuracy .... any time you find a problem after working on anything, the first suspect is something you did

Bill