What's wrong with my tach?

[Guest]

It hasn't worked properly since I got the bike ('83 GS850L); it's very slow when revs are either increasing or decreasing, and I'm not sure it ever reaches the correct value. I pulled out the cable and it was lightly greased, and didn't seem dirty. It's run purely mechanically right, other than electricity for the backlight?

I could live with it not working for a while, but I can't really do my planned (very soon) tune-up work without it. They are still available new, but at $255-$265!

I'm going to make a post in the wanted parts section, but maybe someone has an idea what's wrong with mine, and it can be fixed. Thanks for any thoughts.

Mike

[JT]

Try this thread, It may help.

http://www.thegsresources.com/_forum/viewtopic.php?t=2337&highlight=tach+capacitor

[crag antler]

Have tried to diassemble it and see if the insides are gunged up with any old grease??
That or hook up a drill on low speed and try spinning it to see if all moves freely??
If not, don't give up hope, as I am sure there are others here that maybe able to help more than I :? :? :?

[JMHJ]

Mine has a cable, so I assume it's all mechanical. I haven't taken it off, or opened it up yet, but good idea about the drill. I'll try that first just to see what happens.

[rckrzy1]

I just had the same thing start with mine. I pulled off the black cover and using a dremel cutting blade made an access just above the cable input in the sorta flat horizontal area and then another in the side. I put some triflow (a few drops) on the needle shaft and put a few more on what I call the bell (bell shaped device that magnet pulls on) .

resealed with aluminum duct tape (the metal stuff). And good as new.

[Sandy]

If you need to get inside try this.

http://www.thegsresources.com/garage/gs_inside_gauges.htm

[JMHJ]

Sounds/looks like some quality work. Looking forward to getting mine straightned out. Thanks for the input.

Mike

[Rocketjock]

I took my 80 gs750et tach apart with the same problem. On the square gauge sets they come apart easily. They are purely mechanical and the problem lies with an overly delicate mechanical setup. Mine had taken a slight smack in the past (barely any marks on the gauge housing) and it was enough to knock out the actual tach frame by micrometers. How it works is the shaft is connected to a spinning fat magnetic disk. The actual tach needle is connected to a bell housing that sits over the disk at an angle. When the disk spins, the bell housing slowly rotates. Don't know if this is strictly magnetic action or some sort of gyro effect. In my case it was out of alignment enough that as the bell turned it touched the side of the disk. And that's where it stopped climbing, about 2000rpm. I had it mounted in a bench vise and spun it with a drill so I was able to see it happening. With some ginger bending I was able to straighten it out somewhat. Still not completely satisfied tho. Think my next solution would be to find a used set of guages, spin them up with a drill to make sure they work and replace.

[JMHJ]

Good info. Thank you.

[John W]

My 79 GS850G tachometer had exactly the same characteristics as yours.
Mine is the round orange plastic housing with a metal bezel retaining the glass front.I removed the front metal bezel by prying up the edges with a small screwdriver and a pair of side cutters.Once the mechanism was removed I used a drill to drive the unit ,but could not detect any obvious reason for its sluggish behaviour.I then sprayed the rotating points with an aersol electrical switch cleaner.This cured the problem and the unit has worked normally since.To replace the bezel,I bent it back over the plastic housing using a metal chisel and tapping gently with a hammer.It is not as neat as the factory fitting,but once the guages are back in their housing it cannot be seen anyway.Good luck!

[SqDancerLynn1]

Over the years the grease drys out

[ruddy]

Before you do any surgery on your tach, try removing the whole cable assembly, pulling the inner cable out and flushing the cable housing with something like WD-40. Use some to clean the cable too.

Before lubing the cable, check to make sure the square drive end is securely fastened to the cable. Sometimes they loosen and will spin on the cable causing the symptoms you describe. If it's loose, try some good old JB Weld to fix it. I did this to mine 3,600 miles ago, and it's still working fine. Be sure to thoroughly degrease the parts before you apply the JB Weld.

While you're at it, pull the tach, flip it over and apply some fairly lightweight oil into the opening for the cable end. Not too much so you don't get oil all over the inside of the gauge. :?

Apply some good cable lube, reassemble everything and see if this cures your problem. This is how I fixed my tach, and it was doing the same thing yours is. It's a cheap fix, and worth a try.

[duaneage]

I would not use WD-40 becaue it is a solvent and may attack some plastics. Try and spray Silicone Spray lubricant inside the tachometer and see if that frees it up.

[JMHJ]

Thanks much for the great info. I will let you all know what I find out when I get at mine, once I get a break in family/other obligations.

Mike