Removing a tach needle & unsticking a tach

I have a sticking tach on my XJ1100. It works fine in the summer but 50F & lower it sticks sometimes not moving & sometimes it stays at a number indefinitely. I just received a well working replacement tach mechanism for it and if I can't find out how to best lube the one I have to keep it freely moving at all times, I'll need to replace it.

This poses a couple of questions; the meter plate on the one I received has some scuff marks on it and I'll want to exchange plates, keeping the old & pristine one if I end up needing to use the "new" mechanism. Tugging on the needle I found it was not willing to come off so I need to know how to properly remove the tach needle on one of these.

Any past experience in both lubing a tach successfully and how to best remove the needle without damaging or scuffing anything?

Thanks!

 

Probably your old one just needs lubed.

I've never done an XJ, but had to lube the speedometer jewel on my Venture. On that the needle has a little brass sleeve that presses over the shaft. By holding the back of the mechanism I was able to twist the needle back and forth while pulling to get it off.

You need to find some way to index the needle so you get it back on pointing the same direction. On the speedometer there is a cup on the shaft that I was able to mark to align with a mark on the mechanism. You'll need to look for something similar on your tach.

For a lubricant you want a very light oil.

 

I'm willing to try but I don't know which kind of oil would be best so it doesn't gather dust & then bind up again (was wondering if graphite is a good choice or if it would cause a short in the electronics in there as graphite is an electrical conductor.. Worse, I'm not sure how to get into the guts of the tach unless I remove the cover (where I have to remove the needle to do so). This, because the inner parts of the tach look to be buried inside two halves of the assembly & to get inside this assembly where the bearings or jewel is, the only way to get to the screws holding those two pieces together is to access the heads of them which face the tach meter plate and are inaccessible till the plate is removed.

If they would have had the heads of the screws facing the other way, they'd be easy to get to. Gotta love engineers who don't think of how to help disassembly when they design something...

 

On the 1100 you will find that there a screws on the back side of the white inner case that holds the gauges in place.

Fitz does a similar teardown in his write up here.
Seca 550 Instrument Cluster Teardown with Pics

Fitz gives more info on how to service the gauges here
Speedo and Tach dissection with pics

Any light oil like 3in1, or sewing machine oil should work just fine.

Ghost

 

3in1 or sewing machine oil are not designed for temperature extremes either; you'll be right back where you started.

I use and recommend Tri-Flow: http://www.triflowlubricants.com/Tri-Fl ... icant.html for instruments; it's also an ideal cable lube.

The biggest single factor in successfully removing and replacing a tach or speedo needle is the "indexing" of the needle itself to the cup/spring/shaft assembly that Carl pointed out. Because the needle itself acts as the back-stop for the spring, it it's not positioned 100% correctly the spring won't have the correct amount of preload anymore and the instrument will completely lose any accuracy it once had. The needle HAS to go back on in exactly the same position it started in, relative to the cup and spring.

 

What I do when I pull a needle is this (as far as indexing):

I carfully lift the tip of the needle over the black post. the needle will settle below the post a tiny bit. Then I note how far it is from the post. AFter that, I rotate the needle both ways a couple time and note where it settles in. Usually it's at the same spot each time. Now I now where the needle will be w/o 'preload'. Then I pull the needle off and hopefully it doesn't break (50% of the time). the needle is put back on with the same indexing at the spot after having rotated the needle pin just a tiny bit each way so it can settle in again. The needle goes back on, and I carefully lift the tip over the black post and I'm done.

Never had a problem afterward yet.................

Dave Fox