High frequency vibration/noise: GS550e

[excellentlunch]

Hey all. I picked up an OK running 1978 GS550e with the usual issues (check out my thread in the general maintenance thread) and I have read about the famed top end vibration/noise at 6000 rpm and have noted I get this vibration at about 5400, however, after having a few issues and deciding not to take the 700ks trip back home in its current state, I took it for a little hills blat.

Ran mostly quite well UNTIL it seemed that this vibration was hitting way, way down, like 4500 rpm. I aimed to ride it back home and sort any servicing things then but this has me a little concerned. What could it be? It also stalled from idle shortly after but fired straight back up, but I think the petcock might be a little dicky.

Any ideas and sage advice about riding/not-riding a new-to-me old, worn bike with limited mechanical skills, much appreciated

 

[tkent02]

If it vibrates noticeably at any RPM something isn't right. These 550s are smooth engines. Look for loose motor mounts, foot peg mounts, something big that is loose. Carburetors out of synch will cause vibrations, as will bad ignition, like the timing on one set of points a lot different than on the other. Could also be something like a twisted crankshaft but that's rare on the smaller engines.

You shouldn't ride any bike until all of the maintenance is caught up, ESPECIALLY the valve clearances, tires and brakes. Tires should be replaced unless the date codes indicate they have been recently regardless of how worn they look, brakes should be checked inside and out. Brakes failing is no big deal, but brakes coming on and locking the wheel when you haven't even used them will be bad.

 

[excellentlunch]

Cheers mate. I got myself a van and the GS hitched a ride in the back. It's now safe at home. I did do the brakes beforehand but I couldn't in good conscience ride it that far.

To be clearer about what it is that I'm experiencing it isn't a feeling of vibration but rather a high-ish pitched noise that comes on. I only noticed it at about 5500rpm around town but up in the hills it seemed to be occurring a little lower down, so maybe it's an issue that is developing. Not sure. I will take it for a little run shortly to get a better handle on the symptoms and report back.

Having mucked around with old two strokes it's probably time I got acquainted with all things 4 stroke. Would love to hear any ideas while I dig into the Clymer manual.

 

[SVSooke]

Ditch the Clymer and download this http://zeus.mtsac.edu/~cliff/storage/gs/GS550_77-82_all.pdf and visit the rest of BassCliff's site here http://members.dslextreme.com/users/bikecliff/

 

[TeamNeal]

Is it the bearing in your tach? Maybe...?

 

[excellentlunch]

Is it the bearing in your tach? Maybe...?

That's an interesting idea...

I see you have a 1980 GS550. Does a vibration exist in yours above 6000rpm like this article talks about:

"For a reason which is peculiar to this engine, the 550 emits a very noticeable and irritating high-frequency resonance from just under 6000 rpm until redline. The vibration discourages the rider from high-rpm running for more than about 10 minutes at a time; in the lower rpm range the GS vibrates minimally and is very comfortable."

 

[excellentlunch]

Ditch the Clymer and download this http://zeus.mtsac.edu/~cliff/storage/gs/GS550_77-82_all.pdf and visit the rest of BassCliff's site here http://members.dslextreme.com/users/bikecliff/

Will do! Awesome.

 

[tkent02]

"For a reason which is peculiar to this engine, the 550 emits a very noticeable and irritating high-frequency resonance from just under 6000 rpm until redline. The vibration discourages the rider from high-rpm running for more than about 10 minutes at a time; in the lower rpm range the GS vibrates minimally and is very comfortable."

Been riding GS 550s since 1977, never heard anything like this. I rarely have it under 6,000 RPM because it doesn't make any power until after about 7,000. Wherever this quote came from it's BS.

 

[TeamNeal]

My tach did "squeal" due to the bearing lost lubrication. I heard the noise every so often for short periods, turning into damn near all the time. Couldnt pinpoint it until i was riding a long, straight Texas highway. Then I could go foward, wrap up the Rippms and investigate the source of that sound. Turns out it was the tachometer. ....

I then took it of the cable and top yoke and turned it upside-down. The bearing just lost lube. So I took the tach cable from off the head, reattached it to the tach itself, chucked the cable into my drill and spun her up. Sure enough my hypothesis was proven. Dropped some teflon chain lube on the bearing as best I could and crossed mah digits. Drill spin one more time and noise was gone, at least for a while. Replacement is the fix, relube is just a band-aid so to speak. Try it out, cant hurt.

So

 

[mottacycle]

My tach did "squeal" due to the bearing lost lubrication. I heard the noise every so often for short periods, turning into damn near all the time. Couldnt pinpoint it until i was riding a long, straight Texas highway. Then I could go foward, wrap up the Rippms and investigate the source of that sound. Turns out it was the tachometer. ....

I then took it of the cable and top yoke and turned it upside-down. The bearing just lost lube. So I took the tach cable from off the head, reattached it to the tach itself, chucked the cable into my drill and spun her up. Sure enough my hypothesis was proven. Dropped some teflon chain lube on the bearing as best I could and crossed mah digits. Drill spin one more time and noise was gone, at least for a while. Replacement is the fix, relube is just a band-aid so to speak. Try it out, cant hurt.

So

yup same here put some moly on the tach hook up helped a bit but still squeals

 

[tkent02]

Where exactly did you put the lube?

 

[mottacycle]

Where exactly did you put the lube?

in the hole.... tach hookup under gauge

 

[tkent02]

No that does no good.

You need to lube the space between the inner part that the cable spins, and the outer threaded part that the inner part turns in. There's no bearing or anything, just these two parts, one turning inside the other. With no lube the inner one rattles around inside the outer one, there's your squeal. Use some spray grease like lithium grease that goes in and sets up a little bit. Use the little red straw, shoot it in, it needs to go in a half inch or so. It's easier if you take the gauge off and turn it over but it's not absolutely required.

Don't shoot a ton of it in or the grease will end up on the face plate with the numbers, it's ugly.

 

[TeamNeal]

Ok, so no bearing... whatev. But that is what i was refering to.

 

[tkent02]

whatev, fix the bitch yourself.

 

[mapball]

I remember this article and also disagreeing with it. I love the aggressive howl of the 550 motor. I personally would not consider it an irritating high frequency resonance, but it's certainly not quiet either! Some of the buzzyness might simply be the stock pipes. I swapped mine for a motad 4-1 and the tone become deeper and smoother.