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"wobbly speedo's"

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there have been a few posting queries about speedos that 'play up'. this photo is of a speedo that jumps around at low speeds and i have fixed it by making some small adjustments to counteract wear that has occured over the years. I will try to explain the best i can. In basic terms, the speedo cable drives part 'B' which you can see spins around part 'C'(connected to the needle), there is also a magnet that is connected to 'B' that sits inside part 'C', and is lined up with the metal prongs, as it spins part 'B' pulls part 'C' (which is sprung loaded to return to zero) with it giving you a speed reading--- the speedo cable is not really connected to the needle, it kinda works like a tourque convertor in an auto, IE: one drives the other. Now what happens is that everything rides on the thin shafts 'A' and after 30 odd years , it wears out and causes the mechanisms to rub against each other giving the 'grabbing effect' of the needle jumping up and down, you can ever so slightly and very carefully bend the prongs out to stop them rubbing on the hub (which i have done with this one)-- but not too much as this will effect the reading of the speedo, and that should solve the problem for another extended period of years. sometimes you can get away with packing out the speedo cable with a washer to lift the magnet off the hub, but this doesn't always work.I hope this may help someone, cheers, john
Ps: never touch the speedo face with your hands or you will have a permanent finger print on it.... :)

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Gday John,I have a metric speedo that jumps all over the place once you get over 100 k.I have another in mph.Is there any way you can change the face on them as the mph one works perfectly........Thanks Paul

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g'day paul
to be honest i don't know if the two speedos would be calibrated differently or not
if both are the same type (which they should be) they could be inter changed but whether they would read correctly is debatable.
generally two types of set ups exsist
1 sees the needle rest against a stop when it returns to zero, before removing the needle you would need to release it past the stop, mark the position that it rests at when the spring tension has been released and replace the needle in the same spot and return to the zero position against the stop. If you did not do this then the spring tension would be incorrect and then give a false reading.
the other has the needle at zero without an external stop so it is easier to remove and replace. most needles just press on and off, but understand they are delicate.
again don't touch the faces for finger prints look like [Naughty Pottyword] on them
:bounce:

john
Silence is Non Committal

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Cheers
John
:o)

Dislike me for who I am you may, like me for whom I'm not, you never will...
MY SHED

Should see the bloody speedo in my VH, its stable from about 50 to 75, below 50 it jumps everywhere and over 75 it just drops to 200. I dunno what the hell is wrong with it but its starting to annoy the living crap out of me.

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If you have eliminated all other avenues IE: dry cable whipping, cable not plugged in properly etc. then id say the speedo head is to blame, generally they wear out causing the components to grab together making them jump around, but they can gum up with which a spray of silicon lube can help.
When they play games where it works at some point and then stuffs up at others, really thats a sign that its worn as it will work like this when the components come in and out of balance as they spin, harmonic vibrations so to speak.
Yours sounds like its cactus.
:bounce:

john
Silence is Non Committal

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Cheers
John
:o)

Dislike me for who I am you may, like me for whom I'm not, you never will...
MY SHED

nah its not one of those works sometimes and doesnt others types, its been like that ever since ive been in the car (was my grandads and it was doing it since i was about 10 years old). So yeah its probably what you said, ill check it out when i get some time. Cheers mate

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