Hi all. Changed cambelts about 1000 miles ago as part of normal service routine, using genuine Ducati parts. Have done this plenty of times, so pretty sure I did everything correctly. Had occasion to remove belt covers at the weekend, and noticed that the belt on the vertical cylinder was very slack - the belt on the horizontal cylinder was fine. Have readjusted the belt, and will keep an eye on it, but wondered if the belt is at all faulty (certainly looks ok, but will probably change it anyway). Has anyone experienced anything similar?
I am of the opinion that maybe the vertical belt should be tensioned slightly slacker than the horiz belt.......say, use a 6mm allen key instead of a 5mm........ .........I was astounded at just how tight the vertical belt gets when the engine is hot. So possibly yours has stretched a bit???
Did you use old stock belts: part number ending in 1A or new type ending in 2A? Cant imagine it stretched really, perhaps some oversight when fitting was more likely or the tensioner slipping? Get your new belts here www.exactuk.com and ask for a deal on cables with your purchase here www.exact-start.com
Thanks guys. To answer your points: Arq - it had stretched by more than a 'bit' - could probably have got an 8mm key between belt and roller. I'm sure nothing had slipped (adjuster bolts still tight), but I've never experienced so much stretch before (if you'll excuse the expression!), hence my concern. A bit is to be expected of course, over the service interval, but this goes well beyond that. Exige - the belts are 1A, but newly purchased from DTS in Wakefield, so they ought to be OK - I need to have a chat I think. Thanks for the offer on parts, but have already fitted heavy duty battery/starter cables - well worth the upgrade if anybody is thinking about upgrading. I'll keep you posted.
Will do. I know Paul Klat quite well, and have always had good service, so would expect a positive approach. I'll change the belt anyway, just for peace of mind.
There is always a bit of "bedding in "which results in a slight increase in play on both belts, but never had one become slack by as much as 8 mm so soon after fitting. Thank goodness it was on a two valve.
Wouldn't be overly concerned. The installation tension is just that. Once they've been run, they'll "settle". On the 4V for instance, installation is 110Hz. Inspection is 85Hz or so. Tightening a "used" belt up to installation again is like overtightening from new.
Far more dangerous to over tighten than run slack I think, but for my customers reading this please note installation recommendation is 99Hz on Exact Fit Belts not 110Hz as the OEM belts.
So, what I am construing as excessive stretch ( more than ever experienced before) is not a precursor to belt failure then? That would be my worry.
This is turning into an interesting thread partly because so many imprecise terms/ measurements are being used - just to clarify 8 mm gap ( between back of belt and idler/tensioner bearing) when a reasonable force is applied to pull the belt away and bearing in mind the length of slack between sprockets i.e. where "test " was done, would certainly result in a belt jump on the majority of twin cams i've worked on if *driven with a decent amount of gusto, so ( as said) lucky that this happened on a two valve as you probably wouldn't have got away with it on a four valve *
Agreed. Historically, I've religiously changed belts every two years, and (at the risk of being ostracised!) have always tensioned them as per Haynes, i.e. both at the same time (all 3 sets of timing marks aligned), using a spring balance to exert 4.5kg 'pull' on adjuster pulley. Has always worked without problems, or any signs of stress/distress, over 25k miles. Just this one time with one belt, which is why I'm sort of thinking it may be a (rare?) faulty belt
Gates Technical bod advised me that the belts should be under some tension when cold, otherwise what Chris outlined about a belt jumping is quite likely.
I'm sure that if you check your belts regularly for within tolerance in-service tension, cracks, signs of shredding etc., they will go well beyond the two year mark with no problems. Having said that, it's a brave man who will push it to seven years...
