69" MGB with German Ford Capri 2.8 V-6

[JPB]

If he would answer my question as if its the original MGB speedo or not I could help out.

I have details of how to set it up and roughly calibrate one if it is.

The error is constant so there's nothing wrong with the calibration. As others said, moving the needle around a little will sort this error, which isn't anything to do with the non-original mechanical bits.

[Luxobarge]

If he would answer my question as if its the original MGB speedo or not I could help out.

I have details of how to set it up and roughly calibrate one if it is.

The error is constant so there's nothing wrong with the calibration. As others said, moving the needle around a little will sort this error, which isn't anything to do with the non-original mechanical bits.

No indeed, but the non-original mechanical bits mean he may well need to calibrate it as well.

[JPB]

.....the speedo reads 25 mph at rest and consistently reads 25mph above
actual speed......

That was the bit that my earlier reply was based on.

[3xpendable]

With all due respect, what I meant was that you can't just pull the needle off on these speedos and stick 'em where you want as it wont read properly.

Firstly, I suspect all that's happened is the screw to hold the face in on that side has come loose and wound out, stopping the needle dropping to 0. It happened to me once, and given you say its jammed at around 25mph i'd bet my bottom dollar that's what it is. Look at the image below and you can see the holes for the screws



Failing that, if it ISN'T that issue then to remove the needle you need to take the face off. Once that's done put your finger in the hole that the odometer reset spline goes through until you feel the flat spring of the speedo return. Keep your finger on this and rotate the needle to approx 65mph until you feel a 'notch' in the spring. When you get to this firmly hold the notch be pressing on it with your finger to stop the spring moving then turn the needle back to 55mph (approx), it should then pull off with a gentle tug!

When refitting it, allow the spring to settle, then fit the needle so that the end lines up with that hole below the '0', then gently lift it over the stay and voila. That mark is a rough calibration point so if you line it up the speedo should be fairly accurate.

[JPB]

The o/p didn't say that it was jammed at 25mph, he said that the error is a constant 25mph and not a compounded deviation.

[3xpendable]

Sods law J, I remembered that just after I posted!