Noise from reduction gears? (high mileage STs)

ST1100Y · Sep 1, 2014

My other ST, a '94 with 195Tkm/122Kmiles on, produces a unique sound at idle: the reduction gears of the cam drives are audible, identically on both heads...
(On the daily ride, a '00 with only 90Tkm/56Kmiles, no such noise at all...)

Valve clearances are top notch, no ticking , no clutter, nothing rattling... only a constant "...chchchchchch..." of gears meshing (like "white noise" of a stereo or TV set to a dead channel)
I've already replaced the radial bearings of the shaft for that very reason, no changes, so they were not the cause.
Idler- & spanner-pulley are new, also the w/pump seems rather new (according to the service record had it been replaced rather recently...)
I suspect that due age/miles the springs inside the double-front wheels (the technology intended to reduce the sprocket-clearance thus the gear noise) on the cams are sacking; since there no spares avail, would fixing this require getting new cams...

It basically seems only cosmetically, the bike runs perfect, begs for revs and throttles away like being just stolen from a shop floor, but I wonder if that is an individual case, or if such has also been noticed on other SC26 plants with similar or higher mileage?

STurgisSTeele · Sep 13, 2014

ST1100Y said:
My other ST, a '94 with 195Tkm/122Kmiles on, produces a unique sound at idle: the reduction gears of the cam drives are audible, identically on both heads...
(On the daily ride, a '00 with only 90Tkm/56Kmiles, no such noise at all...)

Valve clearances are top notch, no ticking , no clutter, nothing rattling... only a constant "...chchchchchch..." of gears meshing (like "white noise" of a stereo or TV set to a dead channel)
I've already replaced the radial bearings of the shaft for that very reason, no changes, so they were not the cause.
Idler- & spanner-pulley are new, also the w/pump seems rather new (according to the service record had it been replaced rather recently...)
I suspect that due age/miles the springs inside the double-front wheels (the technology intended to reduce the sprocket-clearance thus the gear noise) on the cams are sacking; since there no spares avail, would fixing this require getting new cams...

It basically seems only cosmetically, the bike runs perfect, begs for revs and throttles away like being just stolen from a shop floor, but I wonder if that is an individual case, or if such has also been noticed on other SC26 plants with similar or higher mileage?

Shoot, I don't have enough experience listening to other ST's to really comment on the sound. But my bike has 130k miles and when I heard my first ST13, I was a bit amazed at how much louder his was compared to mine. His ST really had that Jetson car sound where mine really doesn't. Now, is this because of mileage or the 11's don't have that characteristic to start with? I'm guessing, over time my bike has quieted down. I read recently, that there is an adjustment that when tightened makes the engine louder (in regard to that cool Jetson car sound) and when loosened it is quieter. Could it be this adjustment (sorry, I don't recall where it's made) causing the sound your hearing?

dwalby · Sep 13, 2014

ST1100Y said:
I suspect that due age/miles the springs inside the double-front wheels (the technology intended to reduce the sprocket-clearance thus the gear noise) on the cams are sacking; since there no spares avail, would fixing this require getting new cams...

It basically seems only cosmetically, the bike runs perfect, begs for revs and throttles away like being just stolen from a shop floor,

Sounds like you're looking for a problem where none exists. Could it be random production variations are the cause of the differences you hear between your two bikes, or is there a huge difference?

ST1100Y · Sep 13, 2014

Well, to me its definitely audible... like a worn ball-bearing in an electric motor... a rather significant sound... (maybe why I focus on it... like when hearing it on fan-motors, I know the bearings are done...)
I start to believe that its mileage-, thus wear-related... there >100Tkm/62Kmiles difference between the '94 and the '00...
I might try a different, heavier oil on the next change (currently 5W50)...

dwalby · Sep 13, 2014

So, its not just the fact that there is a sound, its an ominous sound that you associate with impending bearing failure, is that what you're saying? Or is it just a sound that you can't really identify as being a problem, just different from your other bike? If you're already running 5W50, there's not much else available in the oil spectrum, but I doubt that would make any difference anyway. Post a video/audio file on both bikes to give us an idea how different they are.

ST1100Y · Sep 13, 2014

Definitely origins from the forward ends of the heads, thus its the cam drive/reduction...
Will try making some footage for comparison...

CYYJ · Sep 13, 2014

ST1100Y:

By coincidence, I am in Zagreb at the moment, and expect to pass through Vienna Monday or Tuesday (Sept 15 or 16) - I'm riding a 2001 ST1100 with 160,000 km on it.

If you want me to drop by to allow you to listen to my bike for comparison purposes, let me know... either post a reply on this discussion, or send me a PM.

Michael

Jim Van · Sep 14, 2014

I would check the timing belt tensioner pulley bearing, just for S&G's.

ST1100Y · Sep 16, 2014

So, gave it another go tonight, aimed with a mechanic's stethoscope and that...

A similar noise is also present on the '00, very faint though... same sound, same origin (top forward end of the heads)
Cranking the idle down to ~800rpm aids "increasing" it (less load on the gears, lower general engine noise...), adjusting it back to 1000rpm and one has to really concentrate to make it out...

Conclusion:
nothing to be alarmed of, the '94 has twice the mileage, hence more wear, thus increased sound of the cam gears meshing...

Thanx for the attention, when I get both bikes in use again, I'll produce some footage for demonstration.

Noise from reduction gears? (high mileage STs)

When did I become the "Old Man"!?

Michael