sluggish/delayed tachometer readings

[Guest]

1979 GS850G... The tachometer "works" you could say, in that if you have the bike at a constant RPM (or what *sounds* like a constant enough RPM) 15-20 seconds later the tach needle will settle where it *sounds* like it should be.

Example: with the bike off, the needle is at 0 rpm, I start it up, rev it a little and the needle slowly moves up to 3krpm. I let the bike sit at idle and the needle ever so slowly works its way down and ends up around 1100-1200rpm.

The needle seems to go up a lot faster than it goes down. It also never seems to go above 3.5krpm despite the engine being well over that mark by my ear.

I've verified that the tach cable spins/stops when the engine is running/off, so I don't think the cable is broken. I was going to take the tachometer apart but after I got passed the backplate I could figure out how to lift the gauges off the mounting bracket to pull the tack out.

Anyone else run into this? is the tach shot, or could it just be a bad spring or something inside the tach?

Thanks...

[Gonzo]

It could need a good cleaning inside. But before you rip it apart to do that, try lubing the tach. I used some White Lithium grease and shot some into where the tach cable connects and it helped. Don't go overboard with it since you don't want to fill the gauge and get your faces all nasty, but give a shot or two, run it and see how it goes. If that doesn't help, then it just might be time to break her open and clean it up.

[hampshirehog]

Chances are someone has shot some lube up there already and it has gone all sticky. Try lubing the cable first to see if that helps but if not take the thing apart and wipe any sticky old lube off - a cloth dampened with white spirit does the trick.

[spacepirates]

Ok, I'll try lubing the tach cable and spraying lube into the tach housing first.

Is white lithium grease vastly superior to WD40 (which I have on hand)?

Also, my typical cable lubing technique is to spray WD40 down the cable until it runs out the other side, then to drip heavy weight gear oil down through the cable. Will this method suffice?

[Gonzo]

WD40 isn't a lube. Sure, it is a little slick to touch, but it's not a lubricant. It's a mild penetrating fluid and water displacement formula. I don't know what else can be used for the gauges, maybe some of the other guys have some input on what works well too.

[spacepirates]

Gotcha, I'll pick up some spray lithium grease or lubricant and use that.

[1948man]

How do you force the lubricant into the orifice where the cable mates up? Do you use a blast of air? If I turn my gauge upside down and spray teflon lube into that orifice, it just fills up and doesn't want to drain in.

[Gonzo]

1948Man, the WL I bought had a straw that attached to the nozzle. Just attached that and shoot it in there.

If it keeps acting up after a lubing cable and tach, you probably best be ready to gut her open and clean her proper. I think mine are due for a real cleaning, but the lube got me an extra season or so.

[spacepirates]

1948Man, the WL I bought had a straw that attached to the nozzle. Just attached that and shoot it in there.

If it keeps acting up after a lubing cable and tach, you probably best be ready to gut her open and clean her proper. I think mine are due for a real cleaning, but the lube got me an extra season or so.

Is there a guide or forum post about how to do this? I've scoured BikeCliff's site (and the associated how-to sites) and searched this forum but haven't come up with much. I guess I don't really know what to expect in a tach. magic and mysteries ?

[Gonzo]

I haven't seen anything either space. I get the feeling if you or I do it, we would be winging it. Perhaps a good time to take lots of photos and document for a write up.

[rustybronco]

I guess I don't really know what to expect in a tach. magic and mysteries ?

Just a bunch of parts and pieces.

Similar to these... http://i32.photobucket.com/albums/d4...o/PICT3308.jpg

[850GT_Rider]

1979 GS850G... The tachometer "works" you could say, in that if you have the bike at a constant RPM (or what *sounds* like a constant enough RPM) 15-20 seconds later the tach needle will settle where it *sounds* like it should be.

Example: with the bike off, the needle is at 0 rpm, I start it up, rev it a little and the needle slowly moves up to 3krpm. I let the bike sit at idle and the needle ever so slowly works its way down and ends up around 1100-1200rpm.

The needle seems to go up a lot faster than it goes down. It also never seems to go above 3.5krpm despite the engine being well over that mark by my ear.

I've verified that the tach cable spins/stops when the engine is running/off, so I don't think the cable is broken. I was going to take the tachometer apart but after I got passed the backplate I could figure out how to lift the gauges off the mounting bracket to pull the tack out.

Anyone else run into this? is the tach shot, or could it just be a bad spring or something inside the tach?

Thanks...

Where are you at? I may have a tach for you.

[spacepirates]

Where are you at? I may have a tach for you.

Pittsburgh, PA (15120 zip)

[850GT_Rider]

OK. I've got a gauge package from an '80 GS850. Should be same as yours. Speedometer is shot, wiring has been hacked, but tach tests good.

You'd have to do the surgery to pull the tach itself from this setup and use it to replace yours. Think of it as a learning experience

If you want it, you can have it for shipping costs. Should fit in a large priority mail box, so looks like $15.45

Edit: Even before doing all the surgery, you could use this tach to test your bike - make sure the problem is indeed the tach itself.

[spacepirates]

Wow, done deal. Thanks!