A broken motorcycle speedometer can be incredibly frustrating. The number of potential issues seems endless – needle stops working, needle bounces around, odometer stops rolling, etc.. The motorcycle speedometer supplier would give you some amazing news.
The good news is that the trouble-shooting part is relatively easy. In general, you are looking at three potential problems: (1) broken or worn out cable, (2) broken speedo drive, and (3) broken speedometer.
The first one is the one you are hoping for since testing and replacing a cable is very easy.
First, disconnect your cable from the speedometer drive end. For those less familiar with speedometers and how they work – basically there is a single cable that runs from the back of the speedometer to either the transmission or front rotor.
There is a “drive” unit there that spins the inside of the speedometer cable, which essentially tells the speedometer how fast the bike is going (calculated via rotational mathematics – NERD ALERT).
When you disconnect the cable, you should see inside the cable housing a metal cable wire with sort of a “square-ish” shape. Grab your power drill and close the chuck down around the interior cable. First make sure the internal cable looks okay (i.e. that it isn’t broken or frayed).
When the cable breaks, it often breaks at one end or the other. Use your power drill cinched down around the internal drive cable to spin the cable and see if the speedometer needle moves. If it moves, then you know it isn’t your cable or speedometer, but the speedometer drive unit.
On Harley’s like “Cal” these simply unscrew from the transmission, slide out, and can be replaced in just a few minutes. Honestly though a broken motorcycle speedometer usually comes down to the cable first, speedometer itself second, and drive unit third.
If the needle doesn’t move with the whole power drill test, then it is either the speedometer drive or the speedometer itself. This is where you need to borrow a cable from a buddy and repeat the same test.
If your buddy’s working cable makes the speedometer needle move, then it is your cable. If it doesn’t, the speedometer itself needs work. Similarly, if you have a spare speedometer sitting around, you can do the same process of elimination by attaching the good speedometer to your cable. Either way, the whole idea here is process of elimination.
Ultimately, if you find that it is the speedometer itself you have two choices – get a replacement (aftermarket or OEM from a swap meet) or attempt to repair. Truth of the matter is though, that speedometers from Harley were not really designed to be user friendly when it comes to doing a repair.
Put another way, they were not really designed to be disassembled. That said, stay tuned because HappyWrench is going to do a post on how to repair that OEM speedometer. I love challenges and I want “Cal to have an original speedometer.