My Mk1 850 has been laid up for about 3 monthes ,i decided to take it for a run yesterday and noticed when i got going that the speedo was not working, when i got back i checked the cable only to find the inner cable had broken about an inch out of the drive ,so stuck another cable off my other 850 on and needle went to 150mph and stayed there this was just testing it on the centre stand , i now have the speedo on the bench and what is happening is when i insert a screwdriver in the drive hole of the speedo i can wind the needle back and forth from 0 to 150 ,question is does this sound terminal or would it repair, any one else came across this Brian
Speedo stopped working
- Thread starter brf1957
- Start date
- Status
- Joined
- Nov 20, 2004
- Messages
- 20,423
brf1957 said:
Is it Smiths or Veglia? Smiths gauges are certainly repairable but I don't know of anyone in the UK who repairs the Veglia units however I expect there is.
If the needle doesn't return then the needle spring may have broken?
http://members.shaw.ca/randell/Smith/Speedo.html
http://www.speedorepairs.co.uk/
http://www.lulu.com/product/paperback/m ... r/18649253
If its a Veglia the likelihood is the cup that is driven by the rotating magnet and cable has become detached from its brass bushing. What happens is it gets cocked to one side and the magnet makes physical contact with the cup (which it should not). If you are keen and have patience it is possible to repair with basic tools and superglue etc. I did mine and then had Speedo repairs down here do the calibration and glass/bezel replacement.
It could be the second cable either jammed or bottomed out in the the speedo. I don't know the names of the parts involved but the part that receives the cable is maintained at a certain distance from the magnet (disc?) connected to the needle by a thrust bearing. When you tighten the cable housing it loads the bearing, quickly wears it out, the gap is lost, and disc/magnet become fastened by magnetism, then the cable and the needle are basically linked. I got a new cable that needed some modification before it was a slip fit without bottoming.
DogT
VIP MEMBER
- Joined
- Jan 20, 2009
- Messages
- 7,394
The inner cable doesn't want to stick out past the nut that holds it on the speedo when you've got everything else hooked up. If it does, it can damage the speedo. Could be you have put the cable in backwards, don't know. The Smiths are easy to take apart and repair if you have the patience. LAB's links work. You can buy a new bezel and glass and stainless hardware for about $30 in the US. You will have to press the bezel back on by hand unless you know someone that has the tool.
Sending them out is around $250 from what I've seen, but they come back looking like new.
Dave
69S
Sending them out is around $250 from what I've seen, but they come back looking like new.
Dave
69S
- Joined
- Nov 20, 2004
- Messages
- 20,423
The inner cable should not protrude more than 7/16" from the very end of the cable addaptor, when seated, otherwise internal damage to the speedo head occurs. Happened to me on a Smiths on a Triumph many moons ago, cheap Indian cables I think.
Cheers Richard
Cheers Richard
- Joined
- Nov 20, 2004
- Messages
- 20,423
stockie2 said:
7/16" for the "brass cap" Smiths magnetic instruments (below right) used up to around 1970, including Norton "Green blob" instruments. For later Smiths instruments including the "Green globe" (below left) and Veglias it is 9/16", but if in doubt, measure the depth of the drive slot and ensure its deeper than the length of the projecting inner cable.
DogT
VIP MEMBER
- Joined
- Jan 20, 2009
- Messages
- 7,394
This has always worked for me, but I have the Smith's solid green dot early clocks, your mileage may vary.
"The length of cable protruding into the bottom of the instrument is critical. If there is any kind of obstruction which does not allow the lower end of the inner cable to properly enter the drive, then the top end will push too far into the drive mechanism of the instrument and destroy it. We have seen many instances of this. Install the cable at the lower end (remember to secure the outer cover of the speedo cable to the lower side of the swing arm or the end fitting will break off) and examine the top end before fitting it to the instrument. If you slide the knurled nut to its highest position the tip of the inner cable should be exactly level with the top edge of the nut."
Dave
69S
"The length of cable protruding into the bottom of the instrument is critical. If there is any kind of obstruction which does not allow the lower end of the inner cable to properly enter the drive, then the top end will push too far into the drive mechanism of the instrument and destroy it. We have seen many instances of this. Install the cable at the lower end (remember to secure the outer cover of the speedo cable to the lower side of the swing arm or the end fitting will break off) and examine the top end before fitting it to the instrument. If you slide the knurled nut to its highest position the tip of the inner cable should be exactly level with the top edge of the nut."
Dave
69S
Okay so i measured the cable that did the damage and yes the inner cable at speedo end was to long ,so took speedo apart tonight and managed to break glass, i then tapped back the spindle that comes through from the cable end and stuck everything back together and hey presto everything working again, so need to now source new glass and hopefully will be back to normal, have only tried it on the centrestand in the garage so just got to test it on the road yet to see if i have upset the calibration, so thanks to all who contributed advice and info, without that i would not have had a clue ,great forum
- Status
