help me diagnose this engine noise..

[mhobryan]

A little background info - bought this in late fall. odo says 11k miles ... but who knows for sure - unknown history. 1983 850 L. I adjusted the valves, and have also replaced the clutch springs and clutch cable. PO completely rebuilt the carbs, including diaphragms (can tell he went through the trouble to replace all the fasteners, which leads me to believe he did things correct) as well as all exhaust gaskets. I just started to use it to putz around town (had to replace fork seals and the neck bearings), have put about 70 miles on it so far.

Sound is coming from the lower end. Doesn't matter if it is hot or cold, although slightly muted for the first 20 seconds. It does not change when I pull in the clutch cable. I have yet to sync the carbs yet. As you can hear in the video, it is pretty consistent with the engine rpm's. After the first 20 seconds, sounds the same regardless how long I've run it. Trying to determine if this is a serious mechanical issue or not.

Below is a youtube video.

https://www.youtube.com/watch?v=I7m-o9k4PBA&feature=youtu.be

 

[steve murdoch]

Doesn't sound too bad to me.
It MIGHT be the infamous GS cam walk sound. https://www.thegsresources.com/_forum/showthread.php?240997-Cam-walk-options

Another thing to consider is a properly working cam chain tensioner?
Plenty of threads on that.

 

[Cipher]

you sure it not valve clatter? Does it ever go away? Are you listening with a stethoscope or a dowel?

 

[mhobryan]

I'm using a stethoscope. It's very consistent.... can hear it from idle up to about 3k or so....doesn't get louder but the 'clack rate' follows engine RPMs. Louder on the bottom end, and doesn't change when I pull in the clutch...

 

[Steve]

Sounds to me like it's not running on all four cylinders. :-k

.

 

[mhobryan]

Sounds to me like it's not running on all four cylinders. :-k

.

oooh - You may be on to something. I've had two 650G's and both were noticeably more spunky. I know that the 850 (stock) has almost the exact same peak HP and torque ratings, yet is heavier. I expected some degradation of acceleration, but not as much (at least as I remember). If it's only running on 3 cylinders, that would explain it. You've given me something to investigate.

 

[Steve]

Start by making sure all the spark plugs are being fed by the correct wires.

.

 

[mhobryan]

Well, she's firing on all four; validated the plugs are being fed by the correct wires, pulled the plugs, all of the were clean - none were sooty/carbon-y, and all four exhaust headers warm up fairly quickly when started from cold. Also sync'd the carbs...actually, I checked them, and they were close enough that I didn't think I could get them much closer.

Also checked the mpg after running my first half a tank - about 36 mpg mostly city, so figure that's in the ballpark.

Still have the noise though....

 

[mhobryan]

Bump... any ideas on the source of this noise? Or don't worry about it, and ride it like I stole it.

So folks don't have to dig through the thread, below is a link to the video, and a short recap of what's been done:

- using a stethoscope, noise is coming from the lower end of the engine
- noise diminishes the higher the RPM's
- slightly less pronounced when cold, although relatively consistent regardless of temp and riding time
- noise does not change when pulling on the clutch lever
- valves adjusted
- 11k miles
- firing on all four cylinders - wiring correct, all plugs show a normal/healthy firing..nothing sooty
- carbs are sync'ed

I don't believe it is 'cam walk' as it is coming from the bottom of the engine, not the top. I would also assume cam chain noise would also manifest itself as top end noise too...any help / suggestions would be appreciated.

https://www.youtube.com/watch?v=I7m-o9k4PBA&feature=youtu.be

 

[tom203]

"hot or cold, although slightly muted for the first 20 seconds. It does not change when I pull in the clutch cable. "

Maybe something to do with oil pump drive or pump iiself as it builds pressure??

 

[mhobryan]

I decided to take another listen today with the stethoscope. It's coming from the front cam/valve train (more prominent on the left side vs right side)- also had my wife confirm my assessment. After readjusting the valves recently, #1 exhaust allowed my .102 mm feeler gauge through, but not my .12x mm feeler gauge, so left it alone. Therefore, suspect either the loose valve is causing the noise, or possibly the cam chain tensioner needs adjusting.

Edited the feeler gauge #'s .... went out to the garage and double checked - was off by one position. Numbers above are correct. BTW - am very relieved it's not lower end noises!

 

[Nessism]

Sounds normal. Go ride.

 

[mhobryan]

Thanks Nessism, And I will do just that. Although I couldn't leave well enough alone, so decided to readjust #1 exhaust.

Had a 2.50 shim in it, also had a 2.55 in my stash, but that was too thick - my .038 mm wouldn't clear. I had a 'thicker' 2.50 mm shim (had a quality micrometer to check). it made it so that my .102 mm wouldn't fit (it did before), but my .078 mm fit easily. It did quiet it down a bit...had my wife listen (she had to use the stethascope) and said the front (exhaust) cam was making the same amount of noise as the rear (intake) cam. Before she could tell the difference between the two.

So I will now ride it like I stole it.