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I am intrigued by your reference to a Special/ high spec belt.

i have just changed mine and the old one looks perfect. I may stretch replacement to two years. 8k kms is recommended replacement, so that would be about reet.

Right then... i just measured the belt flex as per the suggested guidlines and it was too tight (albeit only slightly). I've put the old one back on for now (correct flex) and the noise has gone, but I'm not entirely sure what to do next? The MDina Italia belt is a type C, which matches both the old belt and the markings on the pulley wheel. I'm assuming that 'type C' is the longest, but appreciate that assumptions are always dangerous

I have just ordered 2 conti belts from RS as they were cheap and easy, but no joy getting them 'sized' as such, so I guess it's just pot luck? Will try them both when they arrive. Any other suggestions (other than earplugs) would be appreciated. I was also wondering if I should have just lived with the noise for a while to see if the belt loosened slightly, but I'm loath to encourage any premature wear on other components.

Incidentally (and perhaps relevant), the bike is very low-mileage (6.5k) and in otherwise amazingly original. And I love it.

And thanks again for being such a great forum.
Tim

When mine whined like a politician I immediately cut it off. I was worried about the stress on the cam and crankshaft bearing. Maybe a bit anal, but not sure it is a good idea to overload a bearing.

Our endless Optibelt Special Edition story in short terms:

In spring of 2007 we have startet an incredible ivestigation/research about our timing belts 124L 075 including contacts to all the producers we could identify like Pirelli (later Dayco selling under the name of Pirelli), Poggi (obviously in former times the oficial Morini supplier, the only one with Moto Morini printed on the belt), Yate, Flender/Flennor, Optibelt ... and also including the tecnical university of Dresden was involved. There is a thread about that investigation of 31 pages on our forum side ital-web.de We collected a big lot of belts from all sorts of producers, intacts, worn, broken and sent them to some of them to investigate and measurements ...

One of the results: there have never been 124L belts from any producer that oficially have been homologated as belts for automobil usage!!!
Investigation at the Optibelt laboratories showed that all of them were made of Cloropren. That means no real/oficial heat and gasolineresistance! They all are/have been industrial belts made for electricaly driven machines. That´s the reason for the suggested interval for changing the belt after 20.000km or at least every two or three years.

Well, we should have at least about 100°C heat restistance, what may be the temperature under the cover of a badly ventilated sidecover of a Dart. Others don´t reach that temperature but more than 80°C may happen easily under the side cover entering a traffic jam coming from a country lane.

After about 10 month two engineers of Optibelt were that impressed by our enthusiasm and tenacity that they offered their help: We could order (minimum 100 belts) some special belts using HNBR instead of Cloropren, the material that is used for bets for automocion rising the heat-, oil-, gasoline and aging resistance in a significant way compared with other polymers. Also with better inner reinforcement glascord (even better than cevlar for this belts). There is no need to change them after 2 years, they last much longer. Obviously they couldn´t be homologated (that process is enormly expensive and we are less than very few customers.) They tried to produce B-belts what is the norm for a 124L. But we had to measure them ourselfs (most of them were B, some C, seldom A).
Our first 200 belts came in may 2008. Since then we could order some more editions (maybe 3 or 4 times in all, the last in 2024, if I remember it well). One of our contacts at Optibelt unfortunatley passed by a couple of years ago. But probably in 2 or 3 years we will try it again.
I think the last ones cost about 30 €. A normal industrial 124 L from Optibelt today maybe at 10 € (don´t know exactly, because I order and store some of the HNBR ones when possible) I´ve used them up to more than 35.000 km and leaving them for 4 years on the bike.

Our invetigation has had another expected result: the very very most common reason for broken belts is their age!!! For the normal industrial belts from Optibelt, that I´ve used for decades, I´ve never paid more than 10 €. And it takes half an hour to change them, when you know how to do. So ... even if it´s a kind of lottery with unmeasured belts the costs of a belt that don´t fit exacty compared with changing timing chains ot belts of a Ducati is ridiculous

That is really interesting. All the technical specs I have seen always quote an upper temperature of 100 oC. Of course that may merely be as far as they test to.

It allways depend on the specific condicions and circumstances what temerature the materials can endure. I´ve read somewhere that chloropren may resist till 100-120 °C, HNBR till 15o°C. Chloropren anyhow is not petrol resistent!!! For examole taking off float chambers may include the risk of weakening the belt structure.
Hartmut has made some testing of the temperature under the right hand cover. He didn´t measure higher temperarures than 87°C even with hot motor in town traffic. Anyhow there are some differences acording to the models of the covers. The first ones have had the best ventilation. Later esp. the front air inlet of the the Enduromodels sidecovers were partially closed (obviously to protect the alternator against mud and water) showing higher temperatures (even from this Enduro air inlets there are differnt models). I would not doubt using the normal industrial belts (at least the Optibelt ones, because never had problems with them) changing them every two years meanwhile they are inside the 6 mm clearance. But I feel better with the HNBR ones when the Optibelt engineers say that they are a lot better. I´m sure Sören has made more mileage than me with this belts

As norbet says in his research the belts are industrial not automotive spec, I fitted an nlm supplied b belt so tight the belt smoked , it was a bog standard over the counter mega dyne isoran which could be bought from any bearing suppliers , at the time I was new to the morini and not clued up, it was inked with the letter b , but way to tight . My own fault really for running with it , bike ran awfull , another thing to be aware of when the engine gets hot the belt gets a bit tighter due to expansion of metal components , a very good idea the straight edge and allen key from morini tom I wish I new that back then , on the advice of ev guru I started using gates power grip belts and all fine , but who knows overtime tolerances change in engines, finding the belt for your engine can be a bit hit and miss, I need to get a ghost writer to put down all my morini gaffs and cock ups I have made over the years its gut churning , but on the bright side me and the morini are still going. Tuto gas muller.