My speedo needle has recently begun to move in a ****y fashion and windshield-wipe in ~10 mph increments. Cable is good, lubrication and drive gearbox appear OK. The instrument labeling is "SSM 5001/034" followed by "1600". It is a 120 MPH unit w/gray face.
Replacement parts book, however, shows BSA #19-8951; SSM 5007/02. Not sure why the difference, as I'm certain the one on the bike is OEM.
I'd like to know the proper ratio and/or suitable substitutes instruments should I decide to replace the gage. Any recommendations on rebuilding services would be helpful, as well. Thanks in advance.