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Discussion Starter #1 (Edited)
Well, after being unable to diagnose this myself, I am putting this out to the collective wisdom of the fourm to help diagnose a strange engine noise from my 2002 ST4s

It started in early May, with a very faint whine or whirring noise that I only heard when the engine RPMs were falling. I went on a ride in the second week in may and at the end of the 600km (400mi) ride, the noise was substantially louder and noticeable all the time. It was loud enough that my passenger even commented that the engine sounded sick.

It sounded to me like a bad bearing, it is rpm dependant, and due to the volume, I thought it was one of the belt tensionser bearings. I've replaced all four of them, and the noise is still there. I've ran the bike with all the clutch plates removed, so the transmission shafts do not turn, and it is still there.

I'm pretty much out of ideas at the moment and was throwing this out if anyone here had experienced something similar.

The bike is a 2002 ST4s, 40,000km (24,000mi) on the motor, and is due for a valve service and belt replacement (have parts, not done yet)

Here's a youtube link to a video I made so you can hear the sound:

http://www.youtube.com/watch?v=4UiKrkzwzo8
 

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Mr Leakered
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LT's manual notes that a galley plug in the crank can back out and hit the engine case. I'm not and expert here, but it sounds right.

How friendly are you with your dealer? They might help get DNA or Duc HQ to get some warranty work.

I think Mark Turbo had this issue if you look at his posts.

Good luck.
 

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Discussion Starter #3
Sadly, I'm not very friendly with the dealer. The nearest dealer is 100km away. I do all my own servicing. If I remember correctly, one of the symptoms of the gallery plug backing out is aluminum shavings in the oil screen.

I checked the oil screen recently, but before this noise popped up and didn't see anything there. I'll pull it again.
 

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Mr Leakered
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I too do all my own stuff also. Splitting cases is something I've never attempted or had to do.

That is what I've heard to look for also. The only other easy, rpm-dependent solutions would be oil or water pumps.

Crossing fingers.
 

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O-oh! A 'whirring' sound eh. Kind of like a supercharger? Yep, I had that on my '02 ST4s at 72,000 miles. Turned out to be a failing main bearing in the bottom end!

My local dealer split the case and discovered the bearing was on the ragged edge of blowing apart (sorry, don't know exactly which bearing, other than it was a main bearing in the bottom end)! If it had failed, it would have caused serious damage in there. Probably terminal damage! Luckily, it was still holding together and they were able to rebuild the engine with new bearings and seals. Considerring the mileage, they also replaced the pistons and resurfaced the cylinders. I now have 77,000 miles on the bike. :D

Sounds like you may have the same problem. Don't take any chances and stop riding it until you diagnose the problem. If a bearing fails in the bottom end, the engine will basically grenade into little pieces in there! :eek:

PS: I just watched your YouTube vide and yes, as far as I can tell, that's pretty much how mine sounded. It is most likely a bearing in the engine that's failing!
 

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Discussion Starter #6
Yeah, It sounded bad to me too. I haven't ridden the bike since I parked it back in mid may. I've only started it up and revved it a bit to try and pinpoint the noise.

I bought a stethoscope to try and pinpoint the noise and I can hear it everywhere I put the scope on the engine case.

Getting 72,000mi out of the engine is pretty good. 24,000mi and having to split cases really sucks.

Well, fixing it now will be cheaper than if it grenades the engine....

Any other suggestions?
 

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No other suggestions I'm afraid other than don't run the engine until it's fixed. I handed mine over to the dealer to repair. If you have an extended warranty, you might be able to get the work completely covered. My rebuild was paid for in full by my extended warranty! I will always buy an extended warranty in the future if I keep a bike longer than the OEM warranty. Mine paid for itself several times over! :D

I suspect that some of the failures we experience have a time component to them as well. Your engine may not have the mileage mine has, but both our STs are from 2002.
 

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Well, at least we know WHAT to listen for now! I pray I never hear it.
 

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I had the left main bearing fail on my 94 Monster. I didnt hear anything but found plastic bits from the bearing cage in my oil. Luckily I caught the problem before the engine grenaded itself.

Do the Desmoquattros have ball bearings or journal types? It was a major job pulling the engine and splitting the cases. But I have done it many times on two stroke dirt bike motors, so it wasnt too daunting of a job.

Mike
 

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Well, fixing it now will be cheaper than if it grenades the engine....

Any other suggestions?
Yes, make sure to run the octane recommended by the manufacturer to reduce the frequency of lower end bearing failure. Detonation is hard on those bearings.

I'm not saying that's what happened here, it could be improper manufacture, but for the small cost difference, I would not risk running the 87 octane.
 

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Discussion Starter #12
Yes, make sure to run the octane recommended by the manufacturer to reduce the frequency of lower end bearing failure. Detonation is hard on those bearings.

I'm not saying that's what happened here, it could be improper manufacture, but for the small cost difference, I would not risk running the 87 octane.
I bought the bike with 5800km on it in 2006. It now has 40,000km. Even though I've ridden it pretty hard, and have the scrapes on the centerstand to prove it, I always filled it with 91 octane, and did the servicing according to the Ducati recommended intervals. Valves were chaecked at 10,000km intervals, and belts changed at 20,000km intervals.

Besides a main bearing, any other thoughts on what the noise could be?
 

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Life is too short to worry !
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Besides a main bearing, any other thoughts on what the noise could be?
You could try the cam-belt idler pulley's , just in case they are running dry and casuing the noise on the over-run when they are not loaded.
Slim chances but worth worth looking at them but if the sound is showing itself on the stetho everywhere it would seem likely a main bearing is the cause.......but its worth a try........you never know
Good Luck
 

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... The only other easy, rpm-dependent solutions would be oil or water pumps.

Crossing fingers.
You've ruled out secondary shaft bearings, and idler pulley bearings, the above mentioned water and oil pump, in addition the cam shaft (and bearings), remain amongst the last possibilities that don't require major open crank-case surgery.

Check these first.

Good luck.
 

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I bought the bike with 5800km on it in 2006. It now has 40,000km. Even though I've ridden it pretty hard, and have the scrapes on the centerstand to prove it, I always filled it with 91 octane, and did the servicing according to the Ducati recommended intervals. Valves were chaecked at 10,000km intervals, and belts changed at 20,000km intervals.

Besides a main bearing, any other thoughts on what the noise could be?
It sounds like you took good care of it and it may just have a bad bearing from the factory. Yours is not the first report of an early 2000 996 with a bad botton end/main bearing. I don't agree that you should use high octane on your low compression 996, because that's known to create carboning that in fact causes detonation, but if you decide on getting it fixed, you'll get to see the combustion chamber's condition to help you decide on future octane usage. Keeping TB's in sync is important too.

Funny you should mention it's louder on trailing throttle, because when a Harley Twin Cam engine is being evaluated for bottom end failures, one of the things to do is to cut the throttle from about 4K in third gear and listen for the "death rattle." You may have a death "whine." I don't know how you ride but you may want to consider not lugging the engine, ie put it under stress/load under 3500 rpms. You may also want to get a lenght of 3/8s" wood dowel and hold it to the engine case and to your ear. You'll be able to better isolate where the noise is coming from. Good luck. :)
 

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Discussion Starter #16
A bit of an update here for anyone that is interested.

I already ruled out the pulley bearings previously.

I've done a bit of work on the bike and have ruled out:

the bearings in side the primary drive gear (took it out, put the side cover back on, ran the engine and it still has the whine.)

Oil pump (installed a spare I had lying around, still sounds the same.)

Water pump bearings (pulled out the waterpump impeller, ran the bike briefly, still whined)

The one thing I haven't totally ruled out in the cam bearings. I did listen to them with a stethoscope, and they all sounded the same, I think it's unlikely that all 8 would go at the same time to produce the whining noise. I also listened to the cam bearings on my 1999 996, which doesn't whine, and they sounded the basically the same as the ST cam bearings. I'm pretty confident that the cam bearings are not the cause. Is there any other way I can check them?

I'm fairly certain myself and a friend will be pulling the motor out of the frame tomorrow.

Does anyone perhaps have a cross reference on the bearing part numbers?
I'm not going to pay the ducati dealer for an SKF bearing I can get from an industrial hardware supplier, for likely half the price.
If nobody has that, I'll just read the SKF numbers off the engine bearings as I pull them out and put together a cross reference if anyone else on the forum needs to do an overhaul on one of these motors.
 
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