81 JOTA SPEEDO CABLE

B

brooky

Junior member
Location
PETERBOROUGH
Hi all ,Happy new year to all ,i am having trouble with speedo cable length ,as in when i put the bike onto main stand the cable is so taught it pulls on the speedo and will fuck it if i leave it (speedo) the cable was or looks new i have had the bike 3 years but only just re assembled it ,Does anyone have or could measure correct length please ,the speedo drive is as high as i can turn it the clocks are std in a std mount the forks are std . TIA
 
Hi Brooky,

And a Happy New Year to you too 👍 as far as I know there are 2 different lengths of cable depending on which fork set up you have, Marzocchi or Ceriani,as a rough guide Motalia shows 840mm for Marzocchi and 750mm for Ceriani.That seems to tie up near with mine which has Marzocchi 😎
 
Schurminater said:
Hi Brooky,

And a Happy New Year to you too 👍 as far as I know there are 2 different lengths of cable depending on which fork set up you have, Marzocchi or Ceriani,as a rough guide Motalia shows 840mm for Marzocchi and 750mm for Ceriani.That seems to tie up near with mine which has Marzocchi 😎
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Thanks for that ,will go out to the garage in a bit and measure ,mine has marzocchi too, all cables are venhill on mine which came on the bike explains why speedo was damaged .thanks for your time regards paul
 
Marzochi forks on 120's have (still) longer cales, mainly due to the longer than 180 Marzo forks but also the calipers can be behind the forks instead of infront and and that reveals a need for a bit more length, 1200TS's and RGA's have another length of cale due to tyhe speedo eing on the left and hence further away, so there could be four or five differring lengths. (my personal advice) Dont buy a cable from Venhill, they are too much trouble and hassle to deal with when the item wont work on your bike. tell us what your bike is in detail.
CLEM
 
You would think that something as simple as a speedo cable would be plain sailing to replace but,there have also been cases where the square drive has come up smaller than the original and so doesn’t drive what it’s supposed to 🤔
 
Measured my venhill cable its 800 mm and yes its smaller on the square into the drive as the last owner had wound masking tape around the end slowly sorting the !!! (Repairs )!!!!!!!!!!!!!!!!!!!!!!!!!!!. there are some fuckwits doing there own easy maintainance .
 
CLEMTOG said:
Marzochi forks on 120's have (still) longer cales, mainly due to the longer than 180 Marzo forks but also the calipers can be behind the forks instead of infront and and that reveals a need for a bit more length, 1200TS's and RGA's have another length of cale due to tyhe speedo eing on the left and hence further away, so there could be four or five differring lengths. (my personal advice) Dont buy a cable from Venhill, they are too much trouble and hassle to deal with when the item wont work on your bike. tell us what your bike is in detail.
CLEM
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clem the bike is a 1981 jota series 2, no fairing , calipers mounted to the front of forks , std clock mounts std marzocchi 38,, forks with the speedo drive on the right side and the venhill cable that came with the bike is 800mm
 
sometimes they work and then when you go over something and the forks bottom it disconects, (on full deflection the inner becomes too short,) very annoying that when aftermarket makers produce something, why the hell dont they get it right? a mate has just had to fit new wings to his Jaguar MK11, originals are no longer available, replicas it has to be, but bejesus on first fitting you could put four fingers under the flange that mates with the top face near the bulkhead, much cutting,, mig welding, grinding and polishing later, they fit, how comes they dont get that right??

My favoured cable supplier is JJ Cables, but so far I have always been able to send them a busted one as a pattern, not sure if they keep records of what is needed on a Laverda.
Might be an idea to get an original from a club mate and get a few made (maybe)
CLEM

JJ cables,
Hillfields farm,
Lightthorne,
Warwickshire,
CV35 0BQ

There is also WWW.cable-shop.NL
0031 (0)652446153
being in Holland does not produce a difficulty for us no EU people as a speedo cable will be well under the £135 threshold for import taxes etc.
 
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Decided to replace both speedo and tacho cables. They are both new venhill cables that came on the bike .guess you get what you pay for as the saying goes .
 
brooky said:
Wow that's a mess .did it lock up the wheel ?or just tear everything off
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Not exactly,it all started when my speedo became erratic then stopped registering, so suspecting a broken cable it was removed and checked out OK.

Decided to check on the worm gear set within the drive housing, applying practically no force at all to the the casting it just sheared off!.....I was gobsmacked! not to mention annoyed........whether it had an undisclosed crack or something who knows but they are obviously a fragile casting so beware if trying to disassemble and keep that gear greased up.

Turns out my issue was a worn square drive where the cable attaches.
 
probably the sqaure drive started off as the wrong size, it is not that well known that the gearbox end of the cable is imperial dimensions and the speedo head end is metric dimensions, this harks back to early SF days when the speedo was made by smiths and obviously had imperial dimensins on both ends, quite why it was carried over to the disc type speedo gearbox is a mystery, I dont think there was ever a model with discs and Smiths speedo, excepting (perhaps) some SFC's, which could have arisen from being parts bin specials that needed the instrument for road registering, a proper SFC would have no need for a speedo.
CLEM
 
I also have an 81 series 2 Jota with Marzocchi forks for which I needed a new speedo cable a couple of years ago. Bought one from Venhill, but it was useless. They had used a 3mm diameter inner, where the original is 3,2mm diameter. When the end was formed to a square it was obviously too small and so just spun in drive at wheel!! They insisted it was correct, with no complaints over many years. They offered to make one according to a sample so I sent the original. They returned something of the right length but made with a 3,5mm diameter inner which they formed to a square for drives but now too big at drive despite evidence that they had ground both ends after forming! I had to resort to filing a little more off at the drive end. Has since worked fine, 7000miles, but they charged double for a special and it was still essentially wrong. I did make some notes someplace regarding all dimensions. For now can only find that the square ends should be 2,75-2,8mm (unworn) across flats. 3,2mm cable is available so no idea why Venhill used 3,5 despite my request being for 3,2 as the sample I sent them!!!!! Will try to find the rest of the data
 
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