Belt tension

[mickj]

I've read a lot about changing the belts on my M1200s and most say the tension is really important to get right. However I've not seen anything on why, no one has said what happens if they are too tight or too loose. Can anyone tell me what could happen if the belt is too tight and if it's too loose.

[Nickj]

Too tight and the belts can fail early as it's dragged over the pulleys, Kevlar is used a reinforcment and that doesn't like being stretched and will start produce fractures in the fibres. Too loose and it will start flapping around, well more resonating and that adds more load to the belts and the reinforcement can fail.
So in both cases they can fail early, snapping is rare but it does happen or if the damage to the belt reinforcement is enough stretch and skip on the pullies especially if they are too loose to start with.

Any fail is a bit of a disaster, you really don't want to see the mess it makes of the piston crown and valves.

I'm sure someone has a toe curling picture or two they'll be happy to post

[Mr Gazza]

You can keep going if only one belt lets go.

[Mark64]

Gates do a belt tension app, no mistakes then, I tested it against a Genuine Ducati belt tension tester and they were identical.

[Dukedesmo]

Whilst you should set them right, I don't think it's that critical to be exact on especially if using frequency as the setting.

For example, set your belts properly and then check them a few months later, they will be looser.

I have a mechanical gauge that I bought for my 916 which works well but it won't fit on a 2v belt as there isn't space so I just use the go/no-go allen key method and never had a problem. I tried the frequency thing but found it too fiddly.

I would err on the slack side rather than too tight though as, I assume, things tighten up slightly when hot.

You may have noticed that belt service life has been extended on newer models, I would suggest mainly for marketing reasons (to reduce the perception of Ducati maintenance being expensive) yet they maintain the same settings for older models, but what is the difference?

Obviously belt quality has improved since the early days and I, for one am quite happy to double the official service life on my bikes.

There, I've said it now and will probably suffer a catastrophic belt failure...

[mickj]

Thanks for all your replies, I changed the belts last month and only took the bike out yesterday for the first time but after only 3 miles I noticed a "tappety noise" hard to explain so I went back home and stripped the belt covers off and I couldn't see anything wrong although the belts seemed to be at different tensions and I did check them twice before putting everything back together. So today I will re-tension them and try again.
Gasa, I don't ever want to see that in my engine.
Dukedesmo, I did strech them to 6 years before changing them but I'm not sure I would go to 10.

[Dukedesmo]

Originally Posted by mickj

Dukedesmo, I did strech them to 6 years before changing them but I'm not sure I would go to 10.

Agreed on not leaving them 10 years but my Ducatis are old models with a 2 year belt service.

My Monster is now on year 4 of that 2 year cycle so I'll probably change them next year.

[jerry]

I now use 4 years for old 2v bikes for belt change and 4 years for my S4

[crawsue]

Changed my belts at 15k mls desmo service 2018…..15 k mls and 5 years later another desmo service and belt change…..belts were in A1 condition ! And Yuasa battery fitted at the first service still going strong…

[Albie]

Originally Posted by mickj

Thanks for all your replies, I changed the belts last month and only took the bike out yesterday for the first time but after only 3 miles I noticed a "tappety noise" hard to explain so I went back home and stripped the belt covers off and I couldn't see anything wrong although the belts seemed to be at different tensions and I did check them twice before putting everything back together. So today I will re-tension them and try again.
Gasa, I don't ever want to see that in my engine.
Dukedesmo, I did strech them to 6 years before changing them but I'm not sure I would go to 10.

Did you measure each belt at their own tdc. If not they will be different. Honestly I prefer a 4v belt change to a 2v unless it's a hypermotard 950.

[mickj]

Yes Albie, I did them at their respective TDC on compression. I redid it all yesterday and turned the motor over via the handle a dozen times and checked again all is correct so it's back together waiting for a dry day.

[mickj]

Had a dry afternoon so I took the bike out for a spin and had no Tappety, tap tap noises, no screeeching noises and the bike didn't go Bang so I'm calling that result.

I used a different tuning app which was much easier to use so that helped a lot.
I found the job quite easy really, the hardest part was refitting the tank, I need longer thinner arms to reconnect the overflow hoses.
Thanks for all your help and advice.

[Mark64]

Which app did you use?

[mickj]

I used guitar tuner - likeTones. Very easy to use and stays open while you fanny about between adjustments.

[Albie]

Originally Posted by mickj

Yes Albie, I did them at their respective TDC on compression. I redid it all yesterday and turned the motor over via the handle a dozen times and checked again all is correct so it's back together waiting for a dry day.

I'm glad. Too many don't and they it won't be far out or I give it a little extra or less honest..