Tacho Full of Treacle

[Chris400F]

My 400/4 had not had much use for a long while before I bought it.
Have got it running but tacho behaves as if it is full of treacle - very sluggish in movement.
I'm guessing whatever lubricant is in it may have hardened with age and/or lack of use.
Any thoughts as to whether this may improve with use or anything I could do to improve the situation.
Alternatively if a refurb may be necessary any suggestions for someone to do it who wouldn't charge the earth.
Thanks.
Chris

[hairygit]

Try a new genuine tacho cable first of all, and make sure it is routed properly and not kinked. If that gives no improvement then the problem is most likely in the tacho itself, but fitting a new cable may well sort it.

[Chris400F]

Thanks for the suggestion.
Cable has already been replaced so it isn't that.
Symptoms are the same when spinning the tacho with an electric drill (running in reverse as that's the direction the cable turns) so problem is with tacho.
I read of someone who dismantled a tacho and cleaned the workings with alcohol. Might give that a try, a new skill to learn.
C

[Bodd]

I wouldn't pay someone to do it, they are easy enough to get apart but if you do clean it with alcohol and get all the old lubricant off what are you going to use as a lubricant ?

I took mine apart when I made some new dials, if you look on this page of my log about 1/4 down the page you will see how I got the clocks apart.

[Chris400F]

Clocks look good in white. I'm guessing the tacho is off something like a G5 with the idiot lights and 9200 red line (400 is at 10000).
No idea what lubricant to use, maybe a light machine oil but sparingly.
Not even sure what alcohol, haven't really looked at what is available yet.
C

[kent400]

The tacho lubrication is only at the drive end, the speedo has shafts and gears that drive the trip and mileage counters that are lubricated. Both gauges have dampers that contain a silicone grease. It could be the case that the damper grease has dried out although that's usual. If there's corrosion on the outside of the base there's a good chance it's corroded on the inside also. As the mechanism contains a rotating magnet rust flakes are attracted that become jammed under the magnet cover. That can cause the problem described.

As for band removal, a hose clip secured around the band prevents it spreading outwards as the edge is lifted from the base. Once the band is lifted a small amount needle nose pliers can be used between the inside edge of the band and the outside edge the hose clip to bring it to vertical. This method can be used on gauge bezels where the glass is housed within them.   

[Chris400F]

Thanks for the hose clip suggestion - that sounds a good tip.
I have another tacho which had obviously been opened in the past without using this trick and the band had spread outwards.
Can't find one large enough in my garage so have ordered a cheap one one from eBay.
Also have got some Isopropyl Alcohol which will hopefully do the cleaning job, have silicone grease already if needed.
C

[Bodd]

You don't need a big clip if you are careful, I've had mine apart again since I originally changed the dials to get rid of the idiot lights in it ( 1/4 way down this page), there was no outward spread either time, I would think a clip would get in the way, patience is the key.