Possibly a stupid question

[harpmeister]

I had to buy a new speedo cable for my RGS, the replacement one has the outer sleeve and the inner cable but I am sure the old one which I have already binned had some other fitment on the end of the cable or am I mistaken ?

Just checking before I take the fairing off.

 

[Dellortoman]

You're absolutely correct. It's a stupid question. How are we supposed to know what the differences are between the old and new cable.

Why on earth did you chuck the old cable out before you got a new one? Even broken cables are useful as a guide to getting the right replacement. By "some other fitment" do you mean some sort of adaptor at one or the other end? You may be getting confused with the tacho cable that has a little fitting that bolts onto the camshaft cover, although I'm not sure about the RGS. I think it might have an electronic tacho.

I'd suggest your best option now is to attempt to fit it. If it doesn't fit or work properly, you might have to talk to the cable supplier to find a solution.

 

[Ventodue]

<snip> but I am sure the old one which I have already binned had some other fitment on the end of the cable or am I mistaken ?

Do you mean a brass ferrule like this? N.B the photo is NOT a RGS cable. If so, it's to stop cable grease getting into the instrument head. So generally a Good Idea.

<snip> although I'm not sure about the RGS. I think it might have an electronic tacho.

You're not wrong Cam, and a piece of fine and accurate measurement it is not ...

 

[harpmeister]

Thanks Ventodue that's exactly what is missing, I tried fitting the cable but without that ferrule it also allows the inner cable to go to far into the speedo drive and that pulls it out of the speedometer slightly causing erratic readings so back it goes to the supplier.

 

[IAG]

I had to buy a new speedo cable for my RGS, the replacement one has the outer sleeve and the inner cable but I am sure the old one which I have already binned had some other fitment on the end of the cable or am I mistaken ?

Just checking before I take the fairing off.

Good advice & a Kiwi scolding compliments of the Laverda Forum!

 

[Dellortoman]

Those little brass ferrules are easy to make on a lathe. But even if you don't have a lathe, you can use a power drill as a poor man's lathe to shape a stub of brass bolt. Drill a hole in it, slide it over the cable and crimp it in place. The dimensions don't have to be perfect.

 

[Ventodue]

<snip> so back it goes to the supplier.

Best, imo. The brass douffa (even if I first used it, 'ferrule' isn't it's correct name; but hey ...*) can, according to some, serve as a limiter for the amount of cable that goes into the speedo itself. Too much, and you can damage the speedo, or so I am led to believe.

So a certain amount of caution is a good thing.

* Ferrule = "A ring or cap, typically a metal one, which strengthens the end of a handle, stick, or tube and prevents it from splitting or wearing." Like this ...

 

[Ian D]

As above, was told by the person who rebuilt my speedo he wanted the cable as well to set the amount that went into the speedo.

 

[andre g]

Those little brass ferrules are easy to make on a lathe. But even if you don't have a lathe, you can use a power drill as a poor man's lathe to shape a stub of brass bolt. Drill a hole in it, slide it over the cable and crimp it in place. The dimensions don't have to be perfect.

good advice

 

[laverda180]

I have also recently run into a speedo cable problem. Bought a new cable for my 81 Jota, has brass ferrule but won’t drive speedo as cable spins in drive shaft at wheel gearbox! I compared new to old cable and found the following:

Old cable dimensions are :

Cable diameter 3,2mm
Across flats (unworn) 2,73-2,83mm
Across flats (worn) 2,58-2,61mm
Across corners (unworn) 3,46mm
Across corners (worn) 2,99mm

New cables:

Cable diameter 2,96mm
Across flats 2,6-2,64mm
Across corners 3,10mm

The drive gear shaft internally measures 3,0mm across flats. Measured using drill shanks as go / no go gauges. 2,98mm diameter shank is go, 3,06mm is no go. The gear shaft may be worn, however it securely drives the unworn section of old cable, but this does not extend beyond outer cable which is why a new cable was required.

I believe old cable was original as I have owned bike since 1986 and approx 20k miles.

Both cables drive the speedo which works just fine.

Could it be that the drive shaft is simply worn out and new cable would be fine if drive gear were replaced?

Can anyone confirm what the dimensions should be for new items? Blimey, what a question for 40+ year old minor parts!

 

[Dellortoman]

I don't know the original internal dimension of the square hole in the speedo cable drive gear. But even if it's a bit worn, it's apparently still within operational limits because it works with the old cable. So I reckon you could fix the problem by building up the square end of the new cable with solder and filing it back to make a larger square. Bear in mind that it may not fit through the outer cable sheath once you've done that, so do it with the inner cable already assembled into the outer.

 

[Paul Marx]

Where did your new cable come from is the question?

Paul

 

[laverda180]

Hi Paul, reputable, well known brand, but they are looking into the situation and will reply. Will wait to see what they have to say. Can only say they offer numerous Laverda speedo cables and from their catalogue descriptions the Delivered item is correct. It installs easily and matches overall dimensions of old cable, but perhaps something did go wrong in selection or build. Will update once vendor clarifies.

 

[piranha-bro2]

There are cases where insufficient length of square end fits into the square hollow which can then allow the inner to spin rather than engage fully.

 

[laverda180]

original cable on its way to vendor for replicating and closing out the problem, hopefully updating his catalogue. I shall request that he does.

meanwhile determined that the original spec was 837mm outer, 875mm inner. Speedo end 2,6mm AF square, 11mm projection at rest (vertical, resting on fibre washer in inner). In this position will have 6mm of engagement in speedo giving full engagement (6mm, axial) in drive at gearbox end with 6mm spare. In event inner rides up this spec results in drive being lost at gearbox just before inner bottoms in instrument so presumably preventing damage to speedo internals. Cable needs to be 3,2mm diameter to achieve a formed 2,8mm AF square drive at gearbox end which will work in my 3mm drive, which is I assume worn, perhaps originally 2,9mm or a little smaller. life Will obviously be reduced compared to the original, but i expect good enough for my needs.

The 2,6mm speedo end can be formed from 3,2dia, alternatively can crimp on a 2,6mm tip If you can find one to suit 3,2mm wire. Must exist, but I could only find tips for 3,7mm wire.

another option if wanting to have a good fit in a worn gearbox is to use 3,7mm wire with crimped on 2,6mm tip at speedo and a modified 3,2mm tip at gearbox. carrot cycles (uk) can supply the bits to make your own.

attempted solder repair of original, but just couldn’t stop cable giving up debris to effect a reasonable deposit of material to file to size.

found a couple of uk vendors prepared to make to spec at great prices. Speedograph Richfield and speedycables.

 

[laverda180]

Took a few months, but finally the vendor supplied a new cable according to my request except they used 3,5mm dia cable instead of the originals 3,2mm ans as I requested. 3.2mm cable can be found online from other retailers! Result was formed ends are large and despite vendor having ground both ends one didn’t fit requiring more filing. Charged me twice the cost of his standard, undersized, 3mm cable as new one was a special, even though I sent him the worn out original to demonstrate that his standard was not to original spec. Too tired to argue. I suspect the new one won’t last long as the formed ends are over stressed and due to grinding / filing the wire that is used to ‚braid’ the cable is now of reduced cross section so likely to break up under load! Happy? No, but at least the speedo functions! Name the vendor? A single bad experience does not a bad vendor make and we need the vendors to keep our machines on the road, so I am inclined to not do so. Our vendors are in the main brilliant. What I learnt was that the drives do not seem to wear, the cables do, and that when a to spec cable is fitted the instruments (ND and never overhauled) will give steady indications with no sign of the dancing needle that I had come to think was normal.

 

[peerfleuren]

You're absolutely correct. It's a stupid question. How are we supposed to know what the differences are between the old and new cable.

Why on earth did you chuck the old cable out before you got a new one? Even broken cables are useful as a guide to getting the right replacement. By "some other fitment" do you mean some sort of adaptor at one or the other end? You may be getting confused with the tacho cable that has a little fitting that bolts onto the camshaft cover, although I'm not sure about the RGS. I think it might have an electronic tacho.

I'd suggest your best option now is to attempt to fit it. If it doesn't fit or work properly, you might have to talk to the cable supplier to find a solution.

there are no stupid questions, only stupid answers??