Snapped belt

[Nasher]

Following on from this:
http://www.ukmonster.co.uk/monster/s...ad.php?t=59962

I collected the bike on Thursday and have had a quick look at the damage.

I thought I'd start a thread with a better tile so that others with a similar issue can find it for reference in future.

Having never seen a snapped Ducati belt before, I didn't really know what to expect, I knew the belt might be shredded, but I wasn't prepared for what looks like the belt exploded in a spectacular way.

Although it should be remembered that the bike was limped home for @5 miles on one cylinder.

Note that before taking the belt covers off I noticed there was a lot of dust and what looked like fibres everywhere that certainly were not there when the bike left me.
By the look of it they've come out of the split in the belt cover.













Both the fixed rollers and tensioner rollers are as free to move as the day I put them in, so a seized roller is not the cause of the problem. Of course they will all be changed again when (possibly if) the engine goes back together.

Although I wasn't expecting the amount of disintegration to the belt, I'm not surprised at all by the split down the middle nature of some of the remnants.
I've never had a car or Ducati belt go in the past personally, but have seen several car and machinery drive belts post snapping.

All the strength is built into the belt longitudinally, with internal stringing in that direction, there is little need to build much strength in widthways.
So when the belt starts to go, it will easily open up like a zipper along the belt.
Compare it to how easy it is to rip a piece of some cloth in one direction but not the other.

I'll get an image of the inside of the belt covers.
There is obvious damage where there was a build up of loose belt around the centre pulley, but no evidence along the cylinder that the belt had moved sideways.

[Nasher]

With the Horizontal piston at BDC to make room for the valves the cam appears to spin over freely enough, with equal resistance to moving the Inlet and Exhaust Valves.
And with the inspection covers off everything appears to move OK, and nothing appears amiss at all.

But, on putting my small Bluetooth Endoscope down the plug hole there is a definite witness mark where the Exhaust valve has touched the piston.

Still feeling lucky I decided to try a compression test using an old set of belts. I'm not sure if they came out of this bike or my M1000DS, but they are perfect to do a compression test without buying a new set of belts.

Unfortunately there is ZERO Compression on the Horizontal Cylinder, compared to a healthy 110psi on the vertical Cylinder.

Being hopeful, it could just be a bent valve, the image from the Endoscope doesn't appear to show any real damage to the top of the piston.

I've soaked the Head nuts, exhaust stud nuts, and those that hold the inlet manifold to the head, in a mixture of Diesel and Acetone, which I'll redo everyday over a few days, then the full extent of the damage will be known when I can get the head off.

I have my M1000 on my lift bench at the moment, and need to finish a couple of jobs on that before being able to get the 1000SS on the lift to make working on it more comfortable.

[Nasher]

Data for those interested
The Belts were Genuine Ducati belts purchased online early last year from one of the well known Ducati independents along with new Tensioner and fixed Rollers.
The Rollers came from Stein-Dinse, but I can't remember who the Belts came from, it was an independent, not Moto-Rapido.
I must dig back through my emails.

They were the first set of Genuine belts I've brought in a while, preferring to use the Exact-fit belts normally, but I think these were on special offer. Perhaps they were old-stock?

The remaining vertical cylinder belt is really badly damaged, but when I get it off I might be able to see the manufacturing date.

Note Exact-fit specify a lower tension than Ducati, but I would have used the Ducati figure.
I use the JPDiag Belt Tension frequency measurement with a small microphone on my laptop, not a phone app.
Sadly the bike had done less than @500miles since.

NOTE:- I do obviously understand there is the chance I cocked this up and put too much tension on that belt.
I will never know.

It was collected on Friday the 15th July, and I think Temps were late 20s early 30s.
It was ridden from my place near Petersfield to just West of Henley-on-Thames, but the guy who brought it was enjoying the bike and went the long way home, I believe completing @100 miles before the bike went on to 1cyl @ 5 miles from his home.

From the discussion he and I had on the phone the bike had got far hotter than I had ever run it at.
20mins after turning it off the indicated temp on the instrument cluster was still 114deg, I'd never seen higher than 110deg when I'd ridden the bike.
Remember that's indicated temp not actual, we all know Ducati Temp gauges are used for comparison not actual temp

Watch this space.

[jamminbmx]

Interesting write up! I have Exact belts on my Monster. Perhaps this is a good reason to stick with them?!

[utopia]

Originally Posted by Nasher

I use the JPDiag Belt Tension frequency measurement with a small microphone on my laptop, not a phone app.

Do you double check the tension via a mechanical method eg allen key method or even 45 deg twist or would you have relied solely on the frequency measurement ?

[Mr Gazza]

Grim reading, but at least you seem to be embracing the task sensibly.

Carl Harrison donated the club a pair of pistons from a 748 a few years back. (Among other parts.)
I polished them up and mounted them on a couple of trophies for the 25th anniversary weekender. It was only sitting outside the Sharnbrook Hotel in the full sunshine that we noticed that each valve pocket was crazed with tiny hairline cracks. I think it was Albie who spotted them?
So I'd had them for months and worked on them studying them quite close up at times during the polishing process and never noticed the cracks!

I just mention this to point out how hard piston damage is to see, but I guess you would probably use crack developer or some such anyway?

Fingers crossed.

[Nasher]

I'd always give the belts a little tweak by hand to see if the tension feels about right, as you say twisting them gives a good indication.

I've given up with the 5 and 6mm Allen key method as I mostly use Exact fit belts that recommend a lower tension.

And despite my initial scepticism, measuring the frequency gives a much more repeatable result.

[Nasher]

Hey Mr G

I wasn't going to bother with crack testing the piston crown, but it could be a good idea.
I'd use my method of Paraffin and talc or chalk dust.

I think that wherever the compression is escaping from must be quite a hole to measure Zero on my gauge, especially as there is actually a decent puff out of the spark plug hole when the engine is turned over with the plug out.

[Albie]

Not that it makes much difference now but the belts should have been a pair manufactured within a short time of each other so can the other belt be checked date wise. Secondly the tension on both belts should have been close to each other so remeasure the other for your own peace of mind. The very fact that the bike was ridden like that for another 5 miles is beyond belief but it has disguised what happened to the belts as they have been completely shredded beyond recognition. We still have this discussion at work about the apps versus other methods but what I'm told in all fairness is that no bike leaving here has had a belt snapped. The pensioners you say all spinning free. These I trust are not flange pulleys . I wonder if one ie the horizontal went off kilt and started shredding that way. Is the belt cover scored at all.
Keep the faith and investigate slowly and dont punish yourself about it.

[the lodger]

Nasher I feel for you mate. I don't mean to highjack your thread but I am just about to fit Exact belts to my M900 . So if they need less tension than Ducati belts , what does the usual 5mm/6mm go/no go allen key/ 45 degrees twist checks reduce to ?

[Albie]

Just because my mind doesn't seem to switch off overnight I'm actually struggling to see where you may have been at fault. You say he did 100 miles before breakage and no doubt you did miles also. I thought the engine itself was bullet proof. You can abuse the clutch and the chain could he have abused the rev range ?. Excited and testing rider ? I dont know but honestly I dont see where it's your fault and it was just unfortunate.

[jamminbmx]

I'm with Albie...I cannot believe how good you are being about this! I brought an XT500 once which had me stuck at the first petrol station on the ride home for 6 hours...didn't even think of calling the ex owner

Hope karma pays you back big time!

[Dukedesmo]

Originally Posted by Albie

You can abuse the clutch and the chain could he have abused the rev range ?

Don't see how any engine abuse could damage a belt? There are belt driven models that rev much higher than a 2v Monster could even dream of, over-revving will put more stress on the valve train and engine internals but not the belts.

Doesn't answer the why though and it is very unfortunate but we can all agree that Nasher definitely went above and beyond the call of duty with his response, well played Sir.

Let's all hope the repair is as straightforward as possible.

[Albie]

Originally Posted by Dukedesmo

Don't see how any engine abuse could damage a belt? There are belt driven models that rev much higher than a 2v Monster could even dream of, over-revving will put more stress on the valve train and engine internals but not the belts.

Doesn't answer the why though and it is very unfortunate but we can all agree that Nasher definitely went above and beyond the call of duty with his response, well played Sir.

Let's all hope the repair is as straightforward as possible.

That's what I'm saying. Simon did the gentleman thing but the unexplained is so frustrating.

[Flip]

Obviously echoing everything the others have said on conduct and certainly on your attentions to detail so I think we can rule out an over tensioned belt for one thing.

What I think needs to be established if possible is why the motor went onto one cylinder before the breakage as that have caused something to go amiss perhaps?

I have only ever known personally of one Ducati to throw a belt and that was a 748 race bike being revved fairly hard to warm up and it just let go.