Problem with Speedo instrument flickering

In my experience you need the lightest lubricant possible. I used to suffer with the wobbly speedo needle and tried various solutions. What worked for me was removing inner cable and washing the outer clean by pouring petrol through it. I then lubricated the inner wire with some very thin lubricant designed for cycles, a sort of dry lubricant once applied. End result has been a rock steady speedo.

I bought this after talking with Vintage British Cables . Apparently this is what they lube their cables with.

Lorenzo said:

what kind of lubricant? WD40? engine oil? grease?

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I've used ordinary grease but don't grease the last 6 inches or so at the upper (instrument) end I suggest that after replacing the inner cable you pull it out a few times and wipe any grease off the inner cable.

Lorenzo said:

what kind of lubricant? WD40? engine oil? grease?

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Sewing machine oil.

Nortoniggy said:

In my experience you need the lightest lubricant possible. I used to suffer with the wobbly speedo needle and tried various solutions. What worked for me was removing inner cable and washing the outer clean by pouring petrol through it. I then lubricated the inner wire with some very thin lubricant designed for cycles, a sort of dry lubricant once applied. End result has been a rock steady speedo.

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can you please show what you used?

I was under the impression that drive cables should not be oiled or greased, but lubricated with graphite.

Lorenzo said:

can you please show what you used?

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I have used both of these at various times.



They do say for chains but they work well on speedo cables.

I currently use the Muc Off one on some other cables. It seems to be just right for throttle cables particularly.

cliffa said:

I was under the impression that drive cables should not be oiled or greased, but lubricated with graphite.

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Not sure why? I replaced mine 5,000 miles ago. As LAB said, I put a light coat of usual automotive grease around the cable. Used the same in the speedo drive on the axle. Avoided the top 6 inches of the cable, to avoid getting anything into the speedo unit. Working fine, so far.

Mart UK said:

Not sure why? I replaced mine 5,000 miles ago. As LAB said, I put a light coat of usual automotive grease around the cable. Used the same in the speedo drive on the axle. Avoided the top 6 inches of the cable, to avoid getting anything into the speedo unit. Working fine, so far.

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Presumably for the same reason you shouldn’t use grease or oil in locks. - They will eventually dry out or create a dirty slime. However it seems most folks just use grease anyway.

cliffa said:

I was under the impression that drive cables should not be oiled or greased, but lubricated with graphite.

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Watch out with graphite aerosol spray, that stuff gets everwhere and seems to take days to get it out from fingerprints....gotta becareful not to commit any crimes for a few days after, the rozzers will be all over you in no time....

Tornado said:

Watch out with graphite aerosol spray, that stuff gets everwhere and seems to take days to get it out from fingerprints....gotta becareful not to commit any crimes for a few days after, the rozzers will be all over you in no time....

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I use a puff bottle ( small ) of bicycle graphite . No pressurized sprays .

Oil should never be used on speedometer cables. It will eventually corkscrew up the cable and contaminate the instrument. It also does not provide the cushioning needed to prevent cable slap and a flickering pointer. Graphite should be avoided. I recommend AGS Sil-Glyde. It is designed for lubricating speedometer cables. It is unaffected by heat and stays put. The lubricating compound and brake lube are the same product, just different packaging. Thick grease would be an alternative. Always wipe the top 6"-8" of inner clean of grease or risk it contaminating the instrument.
Inner cable protrusion is critical, especially with the later Smiths MK2 magnetics (typically the black faces). 9/16" protrusion will damage a magnetic instrument. I consider 1/2" to be maximum. Too long an inner cable is the most common cause of instrument failure.

I know it's an older thread, but this helped me figure out my N15CS issue. It is running a 2" ? longer (Commando, I believe) cable, which isn't ideal, but it was working sorta OK, but jumpy and I didn't like the routing, not 'relaxed' enough. So I fixed it, and broke it.

Background info: The cable is very nice, if a bit long, the speedo professionally rebuilt, and the rear wheel drive unit is a NOS item that I scored.

I took the cable off, lubed it (umm, marine grease which always worked for me, but oh no, an oil thread!), re-routed the cable and screwed the ends in, and it didn't work, no speedo reading at all. Hmm. The measurements here were helpful - I found it was only about 3/16" past the end of the cable housing. Huh? Best I can tell, the bad/wavy routing was pushing the speedo end farther into the speedo, and relaxing it into a better position disengaged it. Ot perhaps some spacer fell out. I don't think so, but it's possible.

I fossicked around in my 'Pile 'O Crap"TM, and settled on a Mikuni carb idle spring as a temp spacer/extender that fit perfectly. I had no suitable washers or spacers so why not? The spring is about 5'16", so it made the end stick out 1/2" at the speedo end, which I think is proper, per this thread. I tested it out with the drill and it seemed fine. Worth a try for the time being, and all is good now, it's much better than before.

Since it was now working, I had to exercise it between 40-80 MPH through the local canyons All's good now until the next thing, I suppose.

I had the same problem as yours. I installed a very small thin washer between the cable and instrument and the problem went away. This brought the dimensions into spec as per L.A.B. diagram above.
Ride On
Dave