I have a MK2 S Speedo which at first seems to be working nicely but then after about 10-15 minutes of driving the needle begins to drop down to zero and bounce back up again then drop to zero then bounce back up again continuously!... it never starts off this way only after a while it starts to behave like this... like maybe the drive shaft inside gets hot and sticks to the sheath or something... I don't know I'm just guessing?? does anyone have an idea what might cause this??

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Jenk.

Plan A
Grease the inner cable.
Plan B
Replace the speedo cable assembly.
Plan C
A trip to a speedo shop.

If you grease the inner cable push it back into the outer sheath and then pull it out about 6 inches and wipe the grease off the cable. this reduces the risk of grease entering the speedo head and that is not a good thing.

RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

Hi I tried silicone spray inside the sheath but still no good! might have to replace cable hopefully that'll fix it but what a PITA of a job from memory.

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Jenk.

If you haven't over tightened the nut on the bottom end of the cable you should be right , put a cable tie around the cable underneath the top nut to stop it pi$$ing off back down the cable when your not looking , that will give you the sh!ts when you think you've nearly got the job finished .

thanks goodie yeah i learned that lesson, the cable tie i used originally is still in place

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Jenk.

Change cable or try a different speedo.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

behaving just like a seizing speedo head.....next is a broken cable followed by a hollowed out speedo pinion in the gearbox.

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....you just lost him his insurance bonus!

997