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Old February 11th, 2017, 10:51 PM   #1
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Cracked Desmo timing gear

Just before Christmas, I picked up my Desmo from its 24,000 km service. The engine, over a period of four months, was stripped down and rebuilt by the Ducati dealership here in Singapore. The guy who did it was factory trained to work on Desmos.
New rings, all new bearings, one new exhaust valve, new seals. The work was comprehensive.
Less than a week after picking up the bike, I took it for a ride and the engine started making a clacking sound on the right-hand-side. At first I thought the clutch had failed.
There was no loss in power. I got home and trucked the bike to the dealership, which spend the next couple of weeks trying to find the source of problem.
Then opened up the timing case and found one of the timing gears cracked in two places -- cracked right through. The gear also seemed to have suffered severe heat.
I've since found out from Ducati Asia and from a very helpful UK Ducati specialist dealership that this particular timing gear has now been superseded to a new part number and the old one is no longer available. Haven't found out why.
The UK specialist also confirmed they had seen a failure like this only once before some years ago. None since.
Anyone suffered this kind of failure or know of a Desmo that has?
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Old February 12th, 2017, 12:27 AM   #2
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Enough is enough

My memory can be pretty ordinary at times but I did remember seeing a thread about timing gear failure. You could consider yourself unlucky or very, very lucky. That was number 500. What number is your bike?

Last edited by Alice Breil; February 12th, 2017 at 12:40 AM.
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Old February 12th, 2017, 01:58 AM   #3
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Enough is enough

My memory can be pretty ordinary at times but I did remember seeing a thread about timing gear failure. You could consider yourself unlucky or very, very lucky. That was number 500. What number is your bike?
Funnily enough, #500 was also in Singapore (engine was replaced in 2009 I think and the new owner recently took it to Australia).

Mine is #1445
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Old February 12th, 2017, 02:00 AM   #4
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And yes lucky in the sense that the gear didn't disintegrate -- I was being very careful with the engine, running it in like a brand new engine.
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Old February 12th, 2017, 04:14 PM   #5
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We must have missed the factory recall notice offering to fit the replacement part at their expense.
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Old February 13th, 2017, 08:14 AM   #6
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Timing gear cracking seems to be a "known thing". When I had my engine top end rebuild, I corresponded with JPH and they specifically recommended checking the gear. It checked out fine at this time. Given the bike is #125, I wonder if it had ever been updated.
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Old February 13th, 2017, 11:03 PM   #7
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We must have missed the factory recall notice offering to fit the replacement part at their expense.
I don't think there's been a recall. Though, sounds like there have indeed been a few failures -- though hopefully no crashes.
Certainly worth getting inspected each major service.
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Old February 14th, 2017, 05:56 AM   #8
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I think Alice was being sarcastic.
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Old February 14th, 2017, 06:41 AM   #9
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To my mind the most important question is :What is causing the timing gears to crack??
Any ideas yet?
How ecxactly have the upgraded gears been modified ?
Unless there were the perfect modifications for the right reasons further issues might occur again.
What more information do we have about this known thing?
Fogs, how many minutes did your engine run after the rebuild ??
Did they run it on the dyno before you picked it up?
When did the noises occur??
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Old February 14th, 2017, 07:05 AM   #10
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ceepee

would cracks like that make the motor sound "clacking", I think cracks as shown would only be audibly obvious when the componant fails
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Old February 14th, 2017, 07:19 AM   #11
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To my mind the most important question is :What is causing the timing gears to crack??
Any ideas yet?
How ecxactly have the upgraded gears been modified ?
Unless there were the perfect modifications for the right reasons further issues might occur again.
What more information do we have about this known thing?
Fogs, how many minutes did your engine run after the rebuild ??
Did they run it on the dyno before you picked it up?
When did the noises occur??
You ask excellent questions and ones that I have also asked. But no one can tell me exactly why mine cracked -- metal fatigue, stress caused by fitting new bearings and rings (causing additional resistance while the new parts run-in), incorrect re-assembly/realignment of parts during the rebuild?
One expert I asked in Germany said the cracks were the symptom of resistance in the valve train or elsewhere in the engine. The engine certainly felt very tight on the road.
I ran the bike for about 70km on the road before the noise started while I was doing about 90 km/h on an expressway. Engine wasn't run on a dyno -- dealer doesn't have one.
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Old February 14th, 2017, 10:23 AM   #12
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Just one quick introduction before trying to go deeper into the subject:
I do NOT intend to lecture anyone but I strongly believe if we do not ask questions analytically technical problems can not be solved.

I would like to find out how often cracks appear shortly after a total rebuild.
Any statistics on that in this forum?

To me the cracks must be the result of missing freeplay between the gears.The gears concerned in this case are the driving gear on the crank and the big timing gear.
Enormous heat is generated.

How will the freeplay needed guaranteed a) at first assembly in the factory
b) after a rebuild

As you say the engine felt tighter than before the rebuild(still with 24k on the clock)the rebuild must have made a difference.
Maybe you ask your mechanic about his feel when fitting(and turning!!!!) the gears.
Again:Make sure he doesn t take your questions personal
If he is sensitive enough he should have a good feel about the resistance in the system,once turned by hand
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Old February 14th, 2017, 08:12 PM   #13
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would cracks like that make the motor sound "clacking", I think cracks as shown would only be audibly obvious when the componant fails

Yes, also a very good question! And it's one I don't think has been fully answered.
The clutch was quickly discounted as the source of the clacking sound and both overhead cam assemblies (lifters, shims, cams, etc) seemed perfectly fine.
The clacking sound could be caused by the cracked timing gear putting stress on the overhead valve assembly in some way. But we're not sure.
Hence the reason I've asked the dealership to strip down the engine to ensure everything is checked, just to be sure all is well.
I'm not suggesting the mechanic failed in his work in any way. He was very diligent. But maybe there are other issues inside the engine we haven't seen that have occurred because of the rebuild or metal fatigue.
There aren't too many Desmo engines with this sort of milege, so in some ways this is journey of discovery for me, the dealership and the factory, which has been consulted on what's happened.
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Old February 17th, 2017, 05:12 AM   #14
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Found the answers yet ?
Any comments from the factory?
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Old February 19th, 2017, 11:00 PM   #15
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Found the answers yet ?
Any comments from the factory?
Hi Michele. No, no update yet from the dealership or the factory. Hopefully later this week.
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