There is debate on if there was a time interval "back in the day" the dealer that I worked at changed belts every 3 years until the new Kevlar belts came out and ducati set the interval to 2 years. I still run them 3 years with no issues. If you are planning on running aftermarkets I would keep the same interval but do inspect them once in a while. 5 years only came in on new 4-valve bikes with much wider belts .
Some do run longer intervals for sure but ask yourself this. Is your motor worth spending $100-300 every few years? if you lose a belt you lose the motor so for me I always recommend my customers play it safe and if you are tight on money I would much rather see aftermarket belts than running belts too long.
I do have a 907 owners manual and in it it states 12,000 miles but NOTHING is listed as time related. They may have not added time requirements at this time but I surely would not chance old belts unless I was willing to replace a motor. At what time is up to you and your avoidance of risk but you can ask members like one in the supersport section that just had a old belt snap if it was worth not changing.
keep in mind the engine is not that different from a late model 2 valve that the factory now claims 2 years on. Something they learned along the way?
the first time a time interval appeared in any workshop manual was 1999 996. before that was only km.
eric - bruce had them changed every 3 years before that? was that based on experience with them failing over longer periods? we'd never heard of any time related changing prior to our first 916 breakage in late 98, or really seen any failures that would make us think of it.
i happily go 4 - 5 years with genuine or exactfit belts.
My 851 had them changed due to miles so no idea on when he brought in the 3 year rule but by the time I started in 1997 3 years was the time we used so it pre-dated the 996. as a fresh out of school mechanic I did not bother asking why at the time just assumed it was ducati spec for many years. We never had belt failures at BCM outside of the odd racer crashing with open belts or someone making a mistake on instal (yes I own that one).
This may have been some of the reasoning as the shop mantra was = make them run as good as we knew they could and make them as reliable as we knew they should have been from the factory. remember the early belts were not expensive so changing belts was not hundreds to do at the time. some of the reason I was not a early adopter of aftermarket belts was because the cost difference was small so why run the knock off and not the oem? Times changed when Ducati dropped about 3 or 4 900 belts down to one and went with the most expensive. truth be told we never had issues with the $30 belts so the $60 belts didn't seem to add anything but costs.
Years ago there was a dispatch rider in England that put 80,000 miles or km (dont remember) on a st2 without servicing the bike.. at all IIRC. Then there will be the bike that loses a part here or there and some times costs more to fix than it is worth.
when i started in 94 my first few days was an official training course with a few old school blokes, and there was not even a mention of time. never heard it at all until that first failure we had, and lots of belts failed on 748/916 out here 99 - 01.
the dealership i worked at went on a strict "must be two years" thing and people would ring the importer's workshop in sydney and ask "why do i have to change my belts every two years?" and they'd get told "we just look at them and if they look ok we put them back in". and then we'd get rung and abused. it was a really badly managed mess out here. bruce was certainly a step ahead of our numpties.
I used to keep track of belt failures in industrial equipment with the intent of reducing down time on a production line . Every now and then when we have a belt discussion here the size of the pulleys gets brought up . I found a greater factor may be disuse. Once a belt is mounted, if it is not rotated periodically it tends to take a set or curve in the direction of the pulley. At this point , bending it in the opposite direction , like many tensioners, creates more stress than if the belt was constantly bent one way. Bottom line is a belt is less likely to fail if it is periodically flexed than if it just sits there in one position, because over time the fibers on the outside stretch more than the inside. Even just cranking your bike over or a few minutes of run time per week can probably reduce chances of failure significantly.
There is enough rubber in a belt and anyone who pays attention to tires knows that age effects rubber, often its ability to flex without cracking. Couple that with duc96cr's post above and you can see where time may be an issue. goldwings had belts with pulleys about 4-5 times the size Ducati uses and also ran at lower rpms usually so this is why they were on more of a automotive schedule. I have not seen any other bike use as tight a belt run except a Britten, do you suppose Britten owners try and extend their belt life as well?
Ferrari's are also listed as 3-5 year service life on belts, but you could treat it like a toyota...lol
I come straight from the Ferrari world where "dis-use" is almost always the norm, meaning some owners would leave the cars not touched for six months. Some time ago, the factory came out with the 3 years timing belt change intervals and the owners were up in arms accusing the factory of loading up their service bays. I personally subscribe to the 5 years interval for my Ferrari. On the bike, I'll go 2 years as factory recommendation. It is not expensive to do. Whereas the engine out service on a Ferrari is 40 hours and $5,000 minimum. That, or a $25,000 engine.
I see way more bearing failures than any other type of belt failure, too tight a belt= bad bearings which ends in bad belts. Simply check them any time the belts covers are off and if in doubt change them. Notched,gritty seized, falling apart and too smooth are all reasons I change them .
i replace so few it's almost a novelty to do so. although i stock the fixed 2v ones these days for 696, etc. wonder if it's a weather thing - they must get condensation in them at times that would freeze in your winters and then rust them? we don't get any freeze, and any hot is way less than running hot so it's not really a thing.
Yes it was a new one on me as well. A couple years ago I had A ST3 fixed bearing that we changed because it was abnormally freewheeling , keep in mind I see these things weekly so touch a lot of them . this bearing on this bike which I have seen many times before spun without any drag that you normally get with seals or grease. The fear was that the bearing was on its way out and the bearing may have bled out its lubrication causing it to have just a touch of extra clearance.
The bearing spun much like any dry bearing without grease or seals except this one had seals and supposedly grease. The customer had spares so i simply swapped it out as he was heading oout on a long trip and always better safe than sorry. This is the bearing that i see fail the most and it is the same one Belter mentions on the 696.
Oddly enough on the older design I almost never changed this bearing it was the tensioning bearings that would net gritty. I am not sure if this is a inferior part or simply the added load of the newer belt geometry. The new part does cost less than the old design so that might be a factor.
Remember I see lots of older pantahs and often they have mixed bag of prior service, many owners do not know what to inspect so by the time I see them they may be anywhere from prefect to a solid non-rolling bearing. It could be condensation build up inside the bearing from hot/cold cycles but it is common to find one of the 2 tensioning bearings not happy. Aftermarket bearings mean you can easily stock/get them but due to the size there are too many options so pick wisely and maybe don't buy the cheapest you can find.
I almost never find the issue on 4-valve bikes it is mostly 20 year old 2-valvers and any/all of the 696-1000ds and newer bikes. Seems as if they went back to the earlier belt geometry there would be less issues with bearings (and hense belts) , maybe next engine revision. yeah not going to hold my breath on that one.