Lower-end noise from my GS850 daily driver

[Roostabunny]

Not sure if you will get the low end (low frequency) rumbles with a stethoscope. Try the piece of wood trick. Push hard against the ear bone. You can hear and feel it all at the same time.

Greetings

Isn't that a scene in Mr. Holland's Opus?

Seriously, though, I will try the stick. I did notice that the sound through the scope seems to be all piercing high frequency stuff.

 

[Roostabunny]

Not sure if you will get the low end (low frequency) rumbles with a stethoscope. Try the piece of wood trick. Push hard against the ear bone. You can hear and feel it all at the same time.

Greetings

This was pretty brilliant - felt like the sound quality was much better with this...

...than with the actual tool (stethoscope).

And I hate to admit it with me calling this a lower-end noise in the first place, but it's prompting me in a different direction. Guess I'd rather fix the bike than feed my ego, so... we'll follow the new data.

First off, I obviously got the bike running. Checked for spark (yes), then drained the #1 carb bowl as I suspected excess buildup from sitting on the side stand for months. Anyway, with a little help from the battery on my Land Cruiser it eventually caught, and with a minor idle speed adjustment warmed up and ran.

First thing I did was take the oil cap off. There was no noticeable difference in sound volume or tone - makes me suspect it's not the clutch.

Then I start with the wooden stick working my way up...
Clutch area - I can hear the tap but not feel it.
Crank/ignition area - seemed a bit louder but still not dramatic
Fins - Not a lot, but might not be enough contact area to get good resonance
Rear of Cam cover (on trim cap) - noticeably louder tapping, some feel through the wood
Front Cam cover (on trim cap) - even louder, felt the tapping distinctly through the wood

I'm still not very confident with this method of troubleshooting, but I did feel like the tapping was more distinct on the right side than the left.

My instinct is to get the cam cover off again and inspect.

Am I crazy not to follow through on pulling the clutch out again and running for a few seconds with no clutch just to eliminate that possibility? Or is the lack of additional volue with the oil cap off enough to say "nope, not the clutch"?

 

[londonboards]

Glad you got on well with the piece of timber.

Looks like you do not have a clutch problem. Especially as you don't get an increase in noise with the oil filler cap removed.

A noise like that on the top of the engine could well be cam end float. This is the cam shaft moving sideways and knocking. There are plenty of threads on this. It is complicated to eliminate and apparently the noise is innocuous and can be ignored. I think there are various symptoms associated with it too. Such as it comes and goes with different engine temperatures. So you might find your noise goes away as the engine warms up but comes back when it is very hot.

I don't think you need to run the bike with no clutch to eliminate that as a noise source. Putting the bike in gear and letting the clutch out until it bites (with the engine running) should tighten up anything rattling down there. If the noise goes when you do that, then have another look at the clutch.

Greetings

 

[Guest]

If it's cam travel the noise should go away when you bring the idle up to 2000 rpm or more. If it is that you can just get used to it and ignore it for the life of the bike. Lots of these bikes have it. There's plenty of YouTube videos describing it as well.

 

[Roostabunny]

Did a closer inspection of the valve train last weekend but didn't see anything noteworthy. I was hoping again to find something out of place or obviously loose, but no.

Edit: I specifically didn't notice any side-play on the camshafts, but not sure if pushing on them by hand is enough to determine.

I'm wondering if...
1.) there's additional troubleshooting I can do without removing the head
2.) if removing the head is even likely to reveal anything
3.) and if I do, what I might look for.

At this point she idles good and plugs seem OK. Bogs a little off idle, but that's new, probably due to too long sitting.

I'm trying not to get discouraged, wish I had a local expert (like I used to in Phoenix) as diagnosing a sound over the internet is obviously pretty tough. I miss riding, but I'm afraid I'll blow her to bits, which isn't much fun or a very safe way to ride.

Another EDIT: Just a question as I keep my options open, best source for OEM base and head gaskets? I'm inclined to go with Z1 if they sell OEM, just checking. And is there anything else I want to do/replace while apart if I do remove the head?

 

[Roostabunny]

After talking with another friend locally, I believe I may be hearing a weak or failed valve spring or other valve train issue.

I'm going to pause this thread and rebuild the top end. It needs to be done anyway (had that seeping base gasket on my hit list for years), and I'm optimistic that I'll find my noise in the process. Wish me luck!

I'll try to document, but not sure yet if I'll create a separate thread for the top end rebuild or just tag it onto this one.

 

[londonboards]

Never a bad thing to do a top end overhaul. Just don't know how you will "see" the cause of the noise. I suppose you could be back to cam chain. Some people insist on replacing the cam chain when doing a top end (using a split one?) and check the cam chain guides and the auto tensioning device.

Good luck

Greetings