Speedo Gear Box - fit or buy new?

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Speedo gearbox has given up the ghost (I think - happy to be educated). I've reseated the cable but still no cable action at all spinning the wheel. Are they worth repairing or just another part of my order to Andover Norton?

I tried lubricating with a heavy oil rather than grease thinking it may be dry grease in the unit.

Ideas?

Find out exactly what bit…

Find out exactly what bit isn't working Can you see the drive spindle revolving in the g/box when you turn the wheel? The cable inner has a nasty habit of rounding off at the square bit, it only engages a short length in the g/box. The gear boxes can be stripped if you have or can make the equipment. Getting the square drive spindle out of the casing means removing the bush at the cable end. I use a slide hammer (the one for rocker spindles) but with an adaptor piece to screw onto the 1/2" x 26tpi thread, heating the casing to break the glue bond on modern units. This is also handy for removing 'seized in the crank case' tacho drive housings.
I have repaired the worn hollow square drive spindle by shortening the spindle and loctiteing a new and better (longer) square drive tube on. If the skew gears are worn its new unit time.
What a lot of people don't know is that the 'push on' grease nipple has a spring loaded ball in it, and with the little 'push to grease' grease gun doesn't develope enough pressure to overcome the spring loaded ball. It just squeezes grease out all over. You think you have got some grease in there but No you haven't. Unscrew the grease nipple to get grease in there and while the nipple is out, remove the ball and spring.

Thanks Peter, inner cable…

Thanks Peter,

inner cable ends are square, and no it doesn't move when the wheel moves.

I put some lighter oil in after removing the grease nipple and spun it round. A nasty silver flecked grey sludge came out that looked like metallic paint. Not good.

Also pushing down on the inner cable to sit in the gear box is positive but I can manually twist the inner cable and can hear it moving something in the gear box - I guess I shouldn't be able to do that without moving the wheel - so I think it's new speedo gearbox time.

cheers

Mick

Almost certainly needs a new one

I'm on about my third one in my Commando's life. The gears wear away. The present one has lasted much longer than the first couple as I am more fastidious about maintenance. You can grease them without fiddling with the nipple if you use a needle point type end on your grease gun. You also need to maintain your speedo cable. It is almost six feet long so can put a big load on the drive if it is not turning easily. I don't use grease on the cable, I use the lightest lubricant I have. It's some stuff sold for lubricating push bike cables and contains PTFE. The added benefit is that the speedo needle is rock steady. If your cable has had grease in it I would remove the inner and pour petrol down the cable to wash it out and wash the inner cable too.

That's a good tip about…

That's a good tip about servicing the cables, I'd not come across it before. Thanks Ian.

Good points Ian - had the…

Good points Ian - had the dirty greasy cable all the way out - being a cyclist too I think you are right about a light lube. Think I'll clean the existing cable down and re lube. Full of 18,000 miles of gunk - may try to rod out the outer while I'm at it.

Fixed Thanks all - new unit…

Fixed
Thanks all - new unit on, outer cable flushed through and drive cable lubed with some PTFE based lube I had knocking around for the push bike.

Now I have a clear and steady speedo.

cheers

Mick

Quality of the Replacement

I assume that the replacements was not made by Smiths, so I wonder how well made these pattern replacement gearboxes are? They are not one of the more robust parts of the bike, even though they have been used by most if not all British manufacturers for decades.

How do they compare to the original Smith's?

Are there any other manufacturers?

I cannot justify the cost of replacement Smiths electronic clocks, which would allow me to remove the gearbox, so it's become a regular strip-down chore, so that it can remain as reliable as it can be.

When pumping grease into a…

When pumping grease into a simple plain grease nipple (the type with no ball to clip the gun to), put a scrap of thin cloth over it first. It seals the edges and stops (most of) the grease from oozing out round the sides.

Top tip David! I don't think…

Top tip David!

I don't think it was an original Smiths unit in the first place.

I can see these as fairly consumable, die cast outer and moving parts never seems to work very well. Will track down the right grease - can see that kicking off another thread entirely! - and see how we go with a lube every 1000.

Will need it more than ever now as I'm through the first 500 miles, just done the first oil change and looking forward to 'half throttle'.

Andover Norton

Hopefully AN will get round to upgrading the speedo gearbox if they haven't done so yet. It's a wretched design.

Norton Owners Club