GPZ 550 Speedo Inaccurate / Tach Not Working

Apologies if this has been covered. I searched for a while and didn't find much info. I recently purchased a 1982 GPZ 550. The speedo needle bounced around on the first day. I lubed up the cable and the worm drive at the front wheel. The needle is now calm but reads high. When I am on the highway the gauge reads 80 and cars are flying by me. My guess it is 10 - 15 mph high. Is there anything I can do about that. I checked the front wheel and tire combo and they are the stock size.

The other issue is the electric tach. It does not work. I appears that I have the signal from the coil at the gauge, the needle just does not move. When I push the volt meter button the needle does not move either. Can these be repaired?

Can someone else with this bike tell me if the speedo is accurate or not?

An inaccurate speedometer isn't unusual on an older bike. Supposedly, the magnets get old & weak over time, resulting in a high reading. Surprisingly, some owners of newer bikes have the same complaint.

I'm not familiar w electronic tachometers. There's probably a troubleshooting section for it in the Kawasaki factory manual.

Yes, like Martin said, you are lucky if a brand new speedo is totally accurate.

I think it's the return spring that gets weak, not the magnet. If the magnet gets weak I would expect it to read low. Seems like, if you can get inside (which is the really hard part), you could try to tension up the spring a little.

The tach sounds dead from your description.

I've never been super successful at putting a tach or speedo back together after disassembly. I did get one mechanical tach back together, but it wasn't pretty.

There should be four wires going into the tach. Check the voltage between the red and black wires. If the voltage there is about 12V and the gauge (in voltmeter mode) reads 0, the gauge is dead. If there's 0V on the red wire, check for open connections. There should also be a white wire and a green wire. The green wire is your pulse signal and the white wire should feed your in-dash light.

Also check the black wire for continuity to the frame (using the ohm scale). If you don't have a good ground, the tach will not work.

Note that the wire colors vary from application to application and may well be different on your specific bike. Check the wiring diagram in your factory service manual for specific-to-your-bike color codes.