Tachometer Stopped Working - Worn Cable End

Saber

Saber

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74 Commando. Original tachometer. New cable from a US supplier in 2019. The needle went to zero on a recent ride. When I got home and checked it out, the finger nut on the gage end was very loose. Like two full turns or more. I tighened it back up and it worked for a few miles and quit again. It was still tight but further inspection showed the gage end of the inner cable is rounded off at the tip. However only 2mm of it is rounded off. I would expect more engagement of the cable than that. I'm contemplating if there is an easy way to get more engagement with this cable so I can use it. Or if I have to get a new one, are there different inner cable lengths that I need to be aware of? Tachometer Stopped Working - Worn Cable End
 
Saber said:
74 Commando. Original tachometer.
Click to expand...

Smiths (RSM 3003/15) or Veglia?

What does the squared end measure across the flats?

There should be a brass(?) sleeve/ferrule crimped to the inner cable which can possibly be repositioned to increase the engagement.
 
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Saber said:
74 Commando. Original tachometer. New cable from a US supplier in 2019. The needle went to zero on a recent ride. When I got home and checked it out, the finger nut on the gage end was very loose. Like two full turns or more. I tighened it back up and it worked for a few miles and quit again. It was still tight but further inspection showed the gage end of the inner cable is rounded off at the tip. However only 2mm of it is rounded off. I would expect more engagement of the cable than that. I'm contemplating if there is an easy way to get more engagement with this cable so I can use it. Or if I have to get a new one, are there different inner cable lengths that I need to be aware of? View attachment 106686
Click to expand...
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Saber said:
74 Commando. Original tachometer. New cable from a US supplier in 2019. The needle went to zero on a recent ride. When I got home and checked it out, the finger nut on the gage end was very loose. Like two full turns or more. I tighened it back up and it worked for a few miles and quit again. It was still tight but further inspection showed the gage end of the inner cable is rounded off at the tip. However only 2mm of it is rounded off. I would expect more engagement of the cable than that. I'm contemplating if there is an easy way to get more engagement with this cable so I can use it. Or if I have to get a new one, are there different inner cable lengths that I need to be aware of? View attachment 106686
Click to expand...

Though this might not be applicable, and the Norton experts here can advise better than me, BMW cars use similar type cables for their seats that "shrink" and I'e been able to stretch them out a little bit. You might try this to confirm it's 100% a cable issue. Of course, someone here will recommend what the best replacement cable is, I've forgotten what new cable I installed in my Commando.
 
Is there anything in the receiver for the cable, eg a piece of snapped off cable end from a previous cable breakage ?
Probably not but worth a look just in case.
 
Thank you gentlemen. Its a Smiths gage. The square cross section is 3x3mm. There is a ferrule at the gage end of the cable that holds the tip to the cable (pic below). It is crimped tight.Tachometer Stopped Working - Worn Cable End There is also a ferrule at the crankcase end but it is slide on / slide off. Not crimped tight. I am going to pull the gage out and use some of your suggestions for a deeper dive.
 
Saber said:
The square cross section is 3x3mm.
Click to expand...

That would be a little slack (metric fitting) as the drive square should be closer to 1/8" x 1/8" (x 3.2mm).


Saber said:
There is a ferrule at the gage end of the cable that holds the tip to the cable (pic below). It is crimped tight.
Click to expand...

If it holds the cable out by approximately 12mm in the picture then there should have been sufficient length to engage with the tacho drive spindle.

Saber said:
There is also a ferrule at the crankcase end but it is slide on / slide off. Not crimped tight.
Click to expand...

I guess you mean the drive spade so that isn't crimped to the inner cable.
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Looking at the 'rounded' tip of the cable - it actually appears it was made that way.
The tip extends 10.4mm when the inner cable is seated in its housing at the gage end. 7.6mm of that is square, the rest is the rounded tip.
It extends 11.2mm when the inner cable is seated in its housing at the crank case end of the cable.
Going by feel, it takes 12mm of extension to start to engage. And bottoms out in the drive spindle about 4mm deeper.
 
I found this little spacer on my bench. Maybe it fell off my cable or an old cable i was looking at. That can get me a little more engagement.
 
Should fix your problem. Had a similar issue with the speedo. Discovered that I was missing a small fibre washer under the ferrule. Lifted the end up enough to engage properly.
 
I have about 6mm between no engagement and fully bottoming out inside the tachometer. With 2 felt washers I am 4mm engaged and 2 mm from bottoming out. Did that and put it back together. Will go for a spin tomorrow
 
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