One of my rockers perforated the cylinder head cover!
 

Guys, today I am an unhappy man:

Yesterday I was doing an evening session at BH (with simon748 - ciao simon) when I heard a noise from the engine and the bike shut down.

Today I stripped everything down and had an ugly surprise:

One of the valve rockers in the horizontal cylinder snapped and, after causing all sorts of damage inside the desmodromic distribution system, actually perforated the cylinder head cover!

I just do not know if the stuck valve (because of the broken rocker) also damaged the piston and the rings...

Three questions:

I had the timing belts replaced less than two months ago and when I saw them today, the tension seemed a bit too loose (approx. 10mm belt swing, measured between the two front/head timing rollers). Is the gap/swing too much? Could that have caused one of the rollers' teeth to "slip" and therefore throw everything off?

Can a rocker brake for no apparent reason?

Can you comment on Pro Team (or Twin?) as the potential workshop to do this work?

Any other comments are obviously welcome...

Ciao, Mario

[Edited on 23-6-2005 by MarioP]

[Edited on 23-6-2005 by MarioP]

Mario,
that sucks the big one - really feeling for you mate.

Pete at PRO-Twins is the man. He is the one to talk to. They are the only people that touch my bike.

Doogalman

Ditto Doogalman.

My guess would be that the broken rocker is a symptom of whats gone wrong, not the cause of it. What might make a rocker break? Well a piston hitting an open valve would do it. Broken belt or belt too loose and jumping a few teeth. Get it back to whoever did the belt change and threaten them!

Pete at pro-twins is a top man and so is the setup. I have had my last two services completed at pro-twins without any problems at all. You might have to wait a few weeks though so book as early as possible.

Guys,

Thanks for all your comments and nice words!

Paul (rockhopper), could the opposite be true: could a stress fracture of one of the rockers cause the belt tension to loosen up a bit?

Just try to understand what could have happened...

Ciao

P.S.: Your avatar keeps reminding me of that damn rocker!!!:mad:

That's seriously bad news, Mario. :o I don't think that a hairline crack in a rocker would significantly affect belt tension, since the pulley don't move in relation to each other. Only the belt tensioner and the belt itself affect its tension. Either it was too loose to begin with or the tensioner pulley has moved somehow.

Most likely scenario is that the cam pullet jumped a few teeth, piston kisses open valve. Even so, it's not usually the rocker that breaks.

Hope the damage is not any more serious than you already know.

Well if the valve is open and the piston smacks it one then something has to give. I have seen rockers break on engines that have been seriously over revved but i'm not sure if the desmo would fail like that. I dont think the broken rocker would affect the belt tension. The head needs to come off really or you might be able to find someone with an endoscope to have a shuftie down the spark plug hole to check for damage to the piston crown.

Wot we need is pictures!

Here you can see where the rocker snapped (top left)

Here you can see how loose the belt is. Is it normal?

Here you can see the damage to the head cover! Powerful stuff...

Here is the "bad guy"...

Here is another view where you can see better where the rocker broke and the damage on the head as well (bottom right)...

Enough, 'cause it is too painful to watch...

So, it's a closer that snapped. Hmmm...do the timing marks on the pulleys still align?

Great question, but do not have the answer...

If they do not, does it mean that a tooth slipped?

The guys who replaced my belt shims will check the bike, but what are the questions I should ask to make sure I understand this was (or was not) caused by a poor belt tension job?

Does the belt tension seem ok in my pics?

I'm probably totally wrong since no one else seems to have suggested it, but wouldn't the belt slacken with a broken rocker anyway?
I mean, if you don't have the valves, rockers etc in contact with each other properly (which you don't, since it's broken) then the cams will move round a tad, thus loosening the belt.
The way to tell is if the timing marks still line up or not when you turn everything into alignment.
I would have thought this was a symptom rather than a cause, because if the belt was fitted wrong, or too loose from fitment I would have thought it would have gone sooner.
Like I said though, I might be barking up entirely the wrong tree!

[Edited on 23-6-2005 by desmojen]

I dont think the belt would slacken becasue of the broken rocker, there are seven others in there to keep everything nice and tight. Plus the belt is tensioned by a pully arangement so unless that had moved there is no way the belt can come loose becasue of things going on inside the head. I've never done a four valve belt change but that amount of slack you have does look excessive.

Like others have said, if the engine will turn over the next thing you need to do is check that the timing marks line up then its head off time i think.

Oh, i just remembered, i have heard of a couple of cases of the main crankshaft belt pully shearing off. Not sure which bikes this happened on though.

My sympathy
Thats going to cost a few bob to put right.

Regards

Nightmare! - I have he technical knowledge of a potatoe so cannot help but hope you get it sorted

Thanks guys!

I am still not 100% that a loose belt could cause a tooth to slip, which in turn could damage the distribution system by having a valve hit the piston, but I have a strong feeling it could be that (also based on what rockhopper said).

Right now the people who usually support me will check if the timing marks line up (trying to figure out what could have happened), and also assess the potential additional damage (e.g. piston crown).

Will keep you posted, since I will have a lot of free time available...

Ciao

Can't believe we didn't see the damage when we first looked at it.Expert help needed protwin or simga are closest both are worth a call.Otherwise it's engine out box it up and send it back to Italy.:flame::puzzled:

Guys, just a quick update on my situation, if you are interested:

My local Ducati people took the cylinder's head off and confirmed that there is a bent valve and a damaged piston. They also told me what caused this was a failure of the rocker and not the loose belts (also confirmed by Ducati factory prototype dept).

I called Ducati factory prototype dept. and explained to them what happened. They said: bring our baby home and we will fix her...free of charge!

Since on my bike there are components that never went into production on the 999 model, they are interested in analysing all these parts and in understanding what went wrong. By the way, they had also left a data logger on my bike (which I did not know about) and they will analyse all my ****-ups on computer now!

I then told them my next prototype will be Desmo16 and they told me to wait until 2006. We'll see...

Ciao and safe riding to everybody.

Mario

Result!

Hmmm, interesting. Cant see it to be honest though. I couldnt make out in your pictures but someone said it was a closer that had broken. I would have thought that the helper spring would have shut the valve and the piston wouldnt have touched it. I guess the broken bit of rocker could have jammed the valve open somehow.

Anyhow, if they are going to fix it all then thats a right result!