Triumph TR6 Broken rev counter

[dumblederry]

Hi Everyone,

I was just wondering if anyone has taken a Smiths Tacho apart, (it's the one with the grey face fitted to most 1969 Triumph / BSA models).
Mine stopped working and after checking the cable was still working I decided to have a look inside   .
Appreciate any advice from anyone who has managed to take one apart and get it working again.

Thanks  

[L.A.B.]

That should be a Smiths 'magnetic' type then?

Can you actually see anything broken inside the unit?

Does the cable drive spindle move up and down in its housing noticeably?

As you have it apart what happens when you push the needle round from zero to the end of the scale. does it return smoothly back to the stop when you let go? Does it actually move back at all?

  

[dumblederry]

Hi L.A.B.

Thanks for your reply

Yes it is the Magnetic type

I have taken off the needle and the clock face.

I am now left with the needle shaft which locates in a small hole in a flat plate but it only just locates in the hole.
under the plate is the rotating magnet.
The needle shaft has a clock type torsion spring that locates on the side of the base plate.

The problem is that it all seem very loose.

Maybe something went missing when it stopped working but without an idea of how it should look I'm a bit stuck.

Thanks
Ron

[L.A.B.]

The problem is that it all seem very loose.

Is it the cable drive spindle that is loose in the housing?
Does it move up and down noticeably? If so then it is probably well worn.

A professional repair may be the only way to get it working reliably again, or you could try to find a good used replacement?  

[dumblederry]

The cable drive spindle looks OK

It seems to be the actual spindle that the needle sits on that's loose.

It is a short spindle about 1/4" long with the spring attached .


I just can't see how it's supposed to locate with the cable drive spindle below.
 

[L.A.B.]

I just can't see how it's supposed to locate with the cable drive spindle below.

It shouldn't physically locate, as it is a magnetic unit.
Is there a metal disc attached to the inner end of the needle spindle behind the dial?

The drive spindle has a magnet at the upper end, and as it rotates it draws the needle disc behind the instrument dial around with it, and thus moves the needle round the dial.
The faster the drive magnet spins the more the needle  moves around the dial, (against the small coil spring's return pressure that moves the needle back when the cable drive slows down).  

[dumblederry]

I see, so it's possible that there is nothing wrong with the needle spindle.
If the drive cable is not engaging corectly then it may not be rotating the magnet to pull the needle spring around.
I will have another look later today and let you know how I get on.
Thanks

[dumblederry]

I have reassembled the unit without holder & glass, attached the drive cable and run it slowly with a battery drill.
The magnet rotates OK so the drive shaft is engaging OK, but there is a lot of vibration especially when you speed up the drive.
the needle does move but only by a few tho revs then starts bouncing wildly.
It seems like It needs a specialist to have a look, any ideas

[L.A.B.]

Not a personal recommendation for either but try:

Gaggs of Nottingham
http://www.totalbikebits.com/tbb_classics/featured_dealer/featured_dealer.htm

Or

Peter Bond

020 8289 9031

peter.bond1@ntlworld.com

31 Avington Grove
London
SE20 8RY

[TBS]

Or Ashley Pople
http://www.speedorepairs.co.uk/

[dumblederry]

Thanks L.A.B. & TBS

I will give them a try tomorrow.

Appreciate the help