tach flutter at highway speeds. problem?

[Anonymous]

My '81 GS450E, 43K miles, has a little phenomenon happening. At highway speeds, the tachometer flutters by as much as two or three thousand rpm. The speedometer is steady, and the engine doesn't really sound like it is revving that much. I have noticed that this happens less when I am coasting at speed, no throttle.

This bike also has a rather noisy clatter at 4300-4700 rpm. I have been advised that it might just be a normal valve rattle, but I just try and stay out of the clatter range if I can.

Possibilities I have considered:

- Harmonic motions causing fluctiations in fuel supply
- Harmonic motions or bad sensor causing false tach reading
- Engine gremlins

I could possible provide digital video of phenomenon if necessary.

So, what is going on and is it a problem?

Thanks,

Michael

[argonsagas]

Tach wobble is usually caused by the cable, not the tach itself.

Problems are

Incorrect or loose fitting, usually at engine end

Lack of lubrication.

Improper routing of cable, causing crimps which affect the ability of the inner cable to turn smoothly.

Fortunately, all of them are easy to check, and correct.



As to the noise....would it, perhaps, sound something like crickets singing?

If so, that is normal for GS bikes.

If otherwise, describe it better, please, as there are are various noises associated with these engines, most of them not a problem.

[AOD]

my 78's bounces on the highway too...

[Anonymous]

I'll start a new topic on the clatter and post an audio clip. I've removed and inspected the tach cable but I haven't checked whether it fixed the flutter.

[Anonymous]

Tup, the tach flutter is fixed. and it seems to just be the cable. I noticed that it was slightly unscrewed from the engine. I removed, inspected, and reinstalled the cable and I think the flutter's fixed.

Thanks, all!

Michael

[Anonymous]

Update: Tach flutter is not fixed.

I noticed that the end of my tach cable looks like the one on the right in this picture.



Could my flutter problem be due to the fact that it should look like the one on the left, but is instead very worn?

Michael

[saaz]

Can't see the pic, but if the end is worn it could cause some variations. Still make sure the cable is routed properly and lubricated.

[Anonymous]

Micheal,

I'd go with Saaz on this one. I had the exact same problem. The tach fluttered 2-3K RPM for about a month and then the cable broke the rest of the way.
I went through the same things your going through. I inspected the cable ... it looked good, checked the conections (all tight). I applied lots of lube and that helped until it failed completly.

Good Luck
Kurt Worden