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MG Midget and Sprite Technical - Correct kmh speedometer for a 1275

We have a 6142/01 speedo with 920 printed on the dial. Is this correct for a 1275? It has been making funny noises which I have rectified with a tiny amount of oil on the worm gear, but it is still reading high on the speed, even though I have reset the needle at the white dot and then pressed the stop wire out of the way to let it set at 0. This is a kmh speedo
dominic clancy

Hi, it is correct for a 1275 according to the Moss catalogue but only up to chassis number GAN466225. After that you would need SN6142/07.

Thanks
Mark
Mark Whitmore

According to Terry Horler's book 6142/01 is a kph speedo for a 4.22 diff. You may well have a 3.9 diff so the speedo will be out and will under-read.
Graeme W

Dominic,
it would have paid you or the car's owner, and still could, to have invested in a copy of Terry Horler's book

Original Sprite & midget The Restorer
Nigel Atkins

According to MGOC I now know this is the correct speedo for the car, and it's over reading with indicated 60kmh when the GPS says 40kmh
dominic clancy

What diff ratio have you got?

Mind you, that error can't be explained by an incorrect differential, more like a knackered speedo.

I agree with Nigel, you really need that book. It's a gold mine of data about what is correct and incorrect about each model. It lists each speedometer and its spec to start with!
Graeme W

" It's a gold mine of data about what is correct and incorrect about each model"

Errors & omissions excepted, as there are some.
Dave O'Neill 2

Dominic,
could it be the wrong speedo cog for the g/box

the odd error in Terry Horler's book wouldn't matter on this car as it a bitsa - and I can say this as I currently own a bitsa and my last Spridget was a bitsa
Nigel Atkins

I have no reason to suspect that there are any wrong parts at play, as the gearbox and engine had never been apart. The gearbox was a wreck off broken teeth, and must have made a horrible noise, but all appeared to be original when dismantled. The rod has obviously been in the grabs for a long time too.
dominic clancy

fair enough just a thought

need more info to check speedo is correct to car - or if you're certain you've correct info about speedo number then it sounds like the speedo possibly needs recalibrating

what number speedo do you have, which model year and country originally for the car, approximate car and/or engine number
Nigel Atkins

I don't think there is an option for the "wrong cog in the gearbox". AFAIK, there is just the one pinion for the 1275 gearbox which drives the output pin shaft to which the speedometer cable connects.

These pinions are notorious for slipping on the shaft (I have that problem) but generally cause major wavering on the speedo needle rather than a steady error.
Graeme W

Car is gan4l 55134, all the other details are in the first post. Car was originally delivered to Switzerland as well.
dominic clancy

oh dear you technical guys, I meant the speedo drive cog, plastic/nylon thing with different numbers of teeth, I think it's called an onion

you really need David Smith looking at his copy of Terry Horler's book and/or factory Parts Catalogue

according to Terry book, if I've read it correctly that number car was a 1967 car not built at Cowley

the 6142/01 speedo is to the 4.22:1 diff

factory Parts Catalogue shows it as part BHA 4437

sorry all this does is confirm the kph speedo

so sorry back to is it the wrong onion or speedo calibration or (like most things in life to me) a mystery
Nigel Atkins

This thread was discussed between 04/08/2014 and 05/08/2014

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