Strange Tach

[jscwerve]

Well, my tach didn't work when I bought the bike a few weeks ago, so today I figured I'd finally replace the cable that was broken in half. Put the brand new cable on and now the tach "sorta" works. When I first start the bike it takes about 5 seconds for the tach to work its way up to idle speed and the needle is VERY sluggish, as in it shows almost no movement whatsoever when revving the engine, and when traveling at speed it won't register anything past about 3500rpm, and does not react to changes in rpms either. I have never seen a tach act like this, so I was wondering what could be causing this. Bad tach itself? spun tach gear in the engine? Is there some sort of clutch mechanism in the tach that prevents it from breaking (like a fan clutch in a car) that could maybe be not locking up? Any ideas are appreciated.
J.C.

[GSstiny]

Mine does the same thing. They were greased internally from the factory. Naturally over 25+ years the grease dries out and interferes with the COMPLICATED mechanism. Nerobro wrote a tech article on how to get inside the housing, or you can just pick up another one on fleabay.

Before you throw money/parts at it, disconnect the cable from the gauge and make sure its turning, that way youll be sure that it is the gauge itself. Id be surprised if it wasnt.

[Suzuki mad]

My GS1000 has the habit of bouncing around at about 4,500 rpm.

There are no clutch mechanisums in the cylinder head to stop the cable braking just a small drive that attaches to the cam shafts and two oil seals. It could be wear on this drive that is causing a problem but more likely it's the rev counter unit thats at fault.

Suzuki mad
GS1000E 1981
GSX1100ESD 1983 nearly back in one peice.

[flyingace]

I just got a cheap JC Whitney tach and it has worked great. Once that delicate mechanism went south, I could not find a way to get it to work again on the stock tach.

[jscwerve]

UPDATE:

Well, I got tired of the strange acting of my tach, and of course I didn't want to buy anything very expensive to replace it, so I took it upon myself to try and fix the problem myself. Thought I'd let everyone know what I did in case anyone else has had this problem.
First, of course I removed the headlight and bucket, and took the guage cluster case apart, front and back. Removed the tach cable and the 2 screws that hold it to the guage cluster, then the tach came right out. noticed that it is actually a pretty simple mechanism consisting of a rotating magnet (rotated by the tach cable) and a metal cup witch gets turned by the magnet spinning inside of it, and that is attached to a spring that returnes the needle to a 0 position when the engine is off, or lower RPMs, etc. I figured it would NOT be a good thing to tamper eith the spring, needle, or anything from the cup to the guage face because I have no idea what the spring tension is supposed to be or even how to get it back together if it was taken apart. There seems to be a set clearance between the metal cup and the magnet, and it looks like it could be destroyed pretty easily with tampering. SO, all I did was clean the magnet, the cup and the coupling for the tach cable with some carb cleaner spray (cover the guage face with something, carb cleaner will probably either melt the guage face or remove the paint, I didn't risk finding out) sprayed the parts till they were shiney new clean! after that I could already see an improvement just by spinning the magnet by hand and seeing the needle respond much faster. Lubed with a bit of dry graphite and put it all back together. works great now. Hope this info helps.
J.C.

[beby99]

Good go'in JC....glad it worked out for you and thanks for the write-up.

[GSstiny]

JC, Im planning to do the same thing, but Im wondering how you got into the tach case. Did you cut it like nerobro? Or pry the metal ring off? Im a little nervous about either considering I dont have a spare.

[jscwerve]

there is no tach case, there are just the two halves of the guage cluster on my 80, after I got the two halves apart, there were only two screws holding the tach into the mounting bucket (if thats what you call it) and it lifted right out. I don't know about other years, but on the 80, everything is open.

[Rocketjock]

If your 80 is the same as my 80 then the tach and speedo are run by a small magnetic (I think) disk spinning inside a bell housing. As the disk spins faster, the bell with needle attached, slowly rotates. I found mine must have taken a bit of a pranging at one time. Just enough so the disk and bell housing were touching at certain RPMs. The frames of those gauges are very flimsy and it doesn't take much to get them out of wack. I was able to somewhat fix mine by bending the bell back into alignment but it wasn't perfect. Better than before tho. Connect a drill to the cable connected to the open gauges mounted in a vise. That way you can see it working.