The numbers I used for correct speed reading
 

I hope it’s ok resurrecting this thread but I’m fitting a similar speedo and hoping for some advice.
The tacho works using a feed from the coil but the needle is slow to react and very jerky.
Is adding a capacitor and resistor the fix for that or was it a fix for the reading being double?
Also, I’ve tried using the fuel level reading for a temperature reading but nothing seems to register. Do I need to add a resistor to fix this?
Thanks in advance for any help. 👍

Which signal did you use for tach?

1. low-level trigger from igniter to coil?
2. high-power output from coil to spark-plug?

Thanks for the reply.
I’ve taken the tach feed from the igniter feed to the coil. It didn’t seem to matter which one I used of the two wires.

In set-up for these clocks, there's typically is menu selection for low-level or
high-level triggers. See what yours is set to and try changing it to other setting.

A resistor is typically only used in-line with high-power coil-output.

These are digital circuits, so tach counts pulses per second. If you have double actual RPM, you need to reduce pulses per second going into tach. This is usually difference
between using sequential vs wasted spark ignition. Again, there's usually settings in clock menu for "# cylinders" or "divide ratio" for pulses to cylinder count. Set this menu to different # cylinders and that should fix RPM ratio.

Cheers but I think the reading is ok, it’s just the needle movement is stiff and jerky, which makes me think it needs smoothing.

I haven’t seen a setting like that for rpm but I’ll check, thanks.

Had a look through the settings menu, no mention of high or low trigger.

The rpm reading is fine, it’s just the needle movement is really jerky. I’ve ordered a capacitor so I’ll try that to see if it helps and report back. Might help someone else with a similar issue.

Still no further forward with using the fuel gauge as a temp gauge either. There are two options for that on the speedo; ‘2 line fuel meter’ or ‘3 line fuel meter’, whatever they mean by that. I’ve tried both and there doesn’t seem to make any difference to the reading.

This is similar to impedance-matching from back in '60s.

Measure your temp-sensor impedance-range. At room-temp and 100C. Most likely range is different. Direction may be different as well since most temp-sensor are NTC - negative temp-coefficient. As temps rise, resistance of sensor goes down.

Compare that to specs for fuel-gauge sensor they're expecting. This one may be expecting resistance to increase as fuel-level goes down.

Then insert resistor if appropriate value in series or parallel to adjust output to match what gauge is expecting.

Thanks for your help so far, been very helpful.

I checked the speedo; disconnected the lead shows 4.6v and the fuel gauge reads empty, if connected direct to earth it shows full. So far so good, it works.

I tried the sensor, at freezing it read 236 (on the 200k scale) and near boiling it reads 11. So I guess that’s going the same way.

How do I know what size resistor to use to get them to match and work properly?