MG Car Repair: Speedometer Error, chrome bezel, fit line

Question
Hello Barrie,

I have a 1971 MGB with a speedometer of 1280 TPM. It consistently reads about 8 MPH faster than I am moving. When The speedometer reads 40 I'm doing 32. When it reads 80 I am doing 72.

I have a 4 speed transmission non-OD.

Any thoughts on how I can correct this?

Thank you,
Denny

Answer
Hi Denny.  You have the correct speedo for your MGB, but the zero setting needs adjustment.  This requires the removal of the instrument from the car:

At your workbench, rotate the chrome bezel until the lugs at the back line up with slots in the casing.  The bezel should then come off, possibly with the glass still attached to it.  If not, remove the glass separately.

With the instrument face upwards, notice that the needle is resting against a wire stop.  Gently press the stop inwards (it should be spring loaded) and pop the needle over it so that the needle is on the wrong side of the stop.

Look carefully at the face of the instrument.  There will be a tiny white dot, and the needle should line up with it.  This is the zero setting.  My guess is the speedo will read about 8mph.    

Carefully pull the needle off its spindle.  It is a taper fit.  Line the needle up with  the spot, then push it back on again.  Make sure it now rests on the spot, or else do it again.

Pop the needle over to its normal resting place and the instrument can now be re-assembled.

Job Done!