Moped Speedometer My Speedometer Doesn't Work What Could Be Wrong?

My Speedometer Doesn't work what could be wrong? - moped speedometer

Hello, left work basically my speedometer on my scooter SYM JET, 1999, I replaced the cable and miles noo, I gather, has not the right speed on the dial. Sometimes it starts at 0 and sometimes begins at 5 miles per hour, where I left off. Please help thank you