Speedometer Reading Incorrect (Low)

Hello, I've seen other posts on this forum where people say their speedo reads too high, and most of the replies say that's normal, however the speedo on my KZ550A has been reading low, which is more worrisome. It read pretty accurately until my recent crash a few weeks ago (I'm fine, bike is fine, don't worry). After making it home, I disconnected and removed the speedo so I could bend and pound the mount back into place. I was pretty shaken up on the ride home, so I didn't notice if it was incorrect right after the crash, or if it happened after reconnecting the speedo, but on my next ride it was reading about 7-10mph below my actual speed, as measured by a roadside radar sign - for example, my speedo read about 30mph while the radar sign showed 38mph. Is there any way I can adjust/recalibrate/repair the gauge to get a more accurate reading? Thanks.

To calibrate your Speedo you have to open the Speedo and adjust the spiral shaped spring attached on the speed indicator shaft. (less preload)

 

There is also a magnetic gap that needs to be a proper size inside the speedo. That gap could be too big now.
Sounds like you'll have to take the speedo apart and see what is bent.
It could be anything that got shakened loose.

Just a thought on this, but sometimes after an impact the needle on the speedo, or tach, can be bent or otherwise damaged. Make sure the needle isn't dragging on the face plate giving you a false reading. Working on speedometers can be tricky at best as usually more damage is done if one doesn't know what they are doing for sure. Years ago I used to take my presumably faulty speedometers in to one of two shops in Milwaukee that specialized in this type of repair work. I don't know if they are still in business or not anymore, if I were a betting man I would bet on they are not in business anymore. You may want to look into the chance of having a speedometer repair service look at your problem child, if you can find a repair shop.

Rick H.

The speedometer gearing is 2240RPM = 60mph. If you have a way of determinaning the input rpm, you can make your adjustment in one shot. Or
see what speed your speedometer reads when being turned with an electric drill. Since you know it reads 20% low, adjust accordingly.