Engine sound ID

[DaveR]

Hello All,

The engine on this new-to-me 79 GS1000 has been slowly given the tune-up procedures as in the FSM. Oil/filter, compression test, carb clean, valve clearances adjusted (except for one), plugs, points adjusted and timing verified. Idles on all four, a bit rough, but I'm still not assured that it's worth committing a pile of cash into.

There is a top end, I believe, "tinking" sound that seems out of place. It is not real loud but is clearly audible over the tappet, camchain and exhaust noise. Does anyone know what this metallic plink could be?

Rode it first time up and down the back alley this afternoon, no seat, tank, or brakes. Man, does this beast have power!!

Thanks, DaveR on the prairie.

[steve murdoch]

It MIGHT be the cam chain.
There is a complete procedure for cam chain tensioner maintenance in BassCliff's tutorials.
Just curious as to why the one valve escaped adjustment.

[DaveR]

Thanks Steve - I haven't checked the cam chain servicing yet. Will look for BCs tutorial, haven't seen that one but have learned a lot from his others.

Short answer why one valve didn't get a new shim? I screwed up ordering.

[SqDancerLynn1]

Could be cam end float - Normal and nothing to worry about..

[DaveR]

I removed the camchain tensioner yesterday and disassembled, cleaned and lubricated it. It is working properly. One more maintenance item serviced and eliminated as a problem. That's progress.

The high pitched metallic tinking is still there and seems to come from the left and maybe rear of the head. Cam walk, from the reading done here, is a possibility but this mild hammering is constant, not intermittent? It appears quieter at cold startup but quickly becomes louder. It does not disappear with rising rpm, at least up to the overall bike sound where it gets lost.

Does anyone recognize the sound from the video? It shows up more clearly near the end and with more treble and less bass. It is more noticeable live than in the video.

All suggestions welcomed.
Thanks again, DaveR on the prairie

http://www.youtube.com/watch?v=-fMhwun6_HE

[steve murdoch]

Could be a clutch rattle?
Does the sound change at all with the clutch lever pulled in? In first?

[DaveR]

There is zero change in the noise with the clutch pulled in or with it in first gear. It seems to be coming from the left top rear of the valve cover.

[omaharj]

Do you have a stethoscope? It may help pinpoint the problem. If you don't,a thin dowel will act as one;one end to your ear,other end touching the engine.

[earlfor]

Sounds exactly like (and in the right place) a loose cam cap. I know that sound.

Earl

[DaveR]

No stethoscope RJ, but a long screwdriver also shows the sound is coming from the left rear valve cover area.

I had really hoped you were right Earlfor. Just back from the shop where the valve cover was removed and all 16 cam cap bolts were found to be tight and to spec. That would have been easy.

There are no scrapes or tick marks on the inside of the valve cover. The only thing I see with my untrained eye are polished marks on the camshaft. The pic is poor but the factory machining is visible where it extends beyond the cam cap. About half of it, about 1mm wide and between the red lines, is highly polished. Is this caused by 'cam walk'? Could this be the source of the constant tinking?

[earlfor]

No stethoscope RJ, but a long screwdriver also shows the sound is coming from the left rear valve cover area.

I had really hoped you were right Earlfor. Just back from the shop where the valve cover was removed and all 16 cam cap bolts were found to be tight and to spec. That would have been easy.

There are no scrapes or tick marks on the inside of the valve cover. The only thing I see with my untrained eye are polished marks on the camshaft. The pic is poor but the factory machining is visible where it extends beyond the cam cap. About half of it, about 1mm wide and between the red lines, is highly polished. Is this caused by 'cam walk'? Could this be the source of the constant tinking?

Run the bike at idle with the valve cover off. Yeah, I know it will be slightly messy. Been there. There is a chance you may be able to see what is moving out of snych with the other moving parts. It sounds like something is striking the underside of the valve cover. If the sound is gone when the cover is removed, at least you will know something is hitting it. You will also be able to tell more distinctly where the sound is coming from.

Earl

[DaveR]

That sounds reasonable Earl. Before that though I took Omaharjs suggestion and went out this morning and picked up a $10. mechanics stethoscope.

I set up 2 fans to blow air on the front of the engine and wow, what a difference in sound complexity compared to a screwdriver. After 10 minutes of listening all around the engine at idle the conclusion is that the sound is not coming from the top end , it's coming from the #1 cylinder. My apologies for steering suggestions incorrectly to the wrong place.

The PO told me he honed the cylinders and lapped the valves 10 years ago, rode it around the block to verify it worked and parked it. He lost interest and went on to other toys and it had not been started since.

I'm flailing about here - could a ring be broken? I am grateful for any and all ideas.

DaveR

[earlfor]

That sounds reasonable Earl. Before that though I took Omaharjs suggestion and went out this morning and picked up a $10. mechanics stethoscope.

I set up 2 fans to blow air on the front of the engine and wow, what a difference in sound complexity compared to a screwdriver. After 10 minutes of listening all around the engine at idle the conclusion is that the sound is not coming from the top end , it's coming from the #1 cylinder. My apologies for steering suggestions incorrectly to the wrong place.

The PO told me he honed the cylinders and lapped the valves 10 years ago, rode it around the block to verify it worked and parked it. He lost interest and went on to other toys and it had not been started since.

I'm flailing about here - could a ring be broken? I am grateful for any and all ideas.

DaveR

I would say a bent valve is likely, but you said you have compression on all four, so I don't think a valve is bent and sticking or striking the piston.
That leaves rings and possibly a wrist pin. The 1100's have roller bearing cranks, and it is very rare for them to knock/fail. In any event, I don't see any way around pulling the head off and the cylinder barrels to have a look see. You're going to need a head and base gasket if you go that route.

You could crank it up and let it idle with the #1 spark plug removed. You may be able to hear the sound better. Or, you could remove all 4 spark plugs and turn the engine over with a wrench. Without it running, the engine being turned over should be almost silent.


Earl

[DaveR]

You could crank it up and let it idle with the #1 spark plug removed. You may be able to hear the sound better. Or, you could remove all 4 spark plugs and turn the engine over with a wrench. Without it running, the engine being turned over should be almost silent.

There was no noticeable difference in the location or loudness with the first suggestion. On the second idea, the engine was quiet and smooth, even listening with the stethoscope, just some sliding (piston?) and soft chain sounds. There was nothing that sounded like the tinking. Oddly, even not finding anything, it's pleasing to be eliminating possibilities.

I picked up a 32mm socket for the front sprocket nut this morning and except for that 2 person job and the engine mount bolts, the engine is ready to remove. Looks like a good opportunity to clean what looks like 32 years of crud and maybe put on a little paint. Will get the oldest son to help grunt when he gets home from work this evening. A findings report later this weekend.

Please don't go away Earl.

[earlfor]

There was no noticeable difference in the location or loudness with the first suggestion. On the second idea, the engine was quiet and smooth, even listening with the stethoscope, just some sliding (piston?) and soft chain sounds. There was nothing that sounded like the tinking. Oddly, even not finding anything, it's pleasing to be eliminating possibilities.

I picked up a 32mm socket for the front sprocket nut this morning and except for that 2 person job and the engine mount bolts, the engine is ready to remove. Looks like a good opportunity to clean what looks like 32 years of crud and maybe put on a little paint. Will get the oldest son to help grunt when he gets home from work this evening. A findings report later this weekend.

Please don't go away Earl.

OK, there is another possibility that would only "tink" when the engine was running at idle rpm or greater. I almost went nuts looking for this one a few years ago. On the stator, when you install it, the wire lead from the windings are put in a channel cast into the side cover. There is a rubber plug that covers the wires where they exit the side cover. About three inches before the wires exit, there is an L shaped hold down bracket that fits in the channel, over the wires, and is held down with one screw. If you do not get that hold down "L' seated in the channel correctly, there is not clearance for the bracket and every time the stator rotates, it will strike the edge of the "L" bracket. It can be a pretty solid "tink" and quite loud. Perhaps the stator has been replaced, or the bracket has come loose. I would pull the left side cover and take a look. If the bracket is hitting, you should be able to see the wear mark. I would check this possibility before pulling the heads and barrels off the engine looking for the cause.

also, once you have the left side cover/stator field assembly off, (the field is bolted to the inside of the cover) you can start the bike and listen for the sound. if it is gone, then it probably is the wire hold down bracket on the field. If the sound is still there, the only thing remaining on the left side of the engine down low is the starter clutch. The starter clutch is held in place by three flush machine screws. one or more of the screws may be broken and allowing the clutch assembly to bang around. You're going to need a rotor puller to get to it though. Don't even consider trying a three jaw gear puller. If the problem is the starter clutch, it should be apparent in starting the bike a few times. The noise location without the side case in place should be obvious.



Earl