Belt tension Allen key?

[koko64]

Yes that ensures timing accuracy, however, that assumes the timing is correct from the factory, which it often isn't.

[MonsterHPD]

I would have a Ducati dealer tighten the belts withe their harmonic tool and them make your tool to match.  You may surprised how tight the belts are.  My opinion is that the motor runs better with tight belts.  You can feel the difference.

As mentioned, this is basically what I did, and as you point out, I was also surprised at how tight the belts were. I've now modified my sleve to 2.5 mm, I'll check where that takes me next time I have to belt covers off.

[Howie]

As mentioned, this is basically what I did, and as you point out, I was also surprised at how tight the belts were. I've now modified my sleve to 2.5 mm, I'll check where that takes me next time I have to belt covers off.

What spec ate you using?

[MonsterHPD]

Well,
to be honest, I don't quite remember what we used at the time, the instrument owner was present and guided, but it was in the 100Hz to  maybe 120 Hz range, new belts. I think the HYM1100 spec is 140/100 Hz new/used belts. Anyway, the belts were quite tight, no convenient way ro get a 5 or 6 mm allen key through. Not impossible, but not convenient or "gagelike".

[Howie]

At some point Ducati went to a lower frequency on some models due to bearing failures.  I don't think Ducati uses 140 for anything at this point.

[MonsterHPD]

At some point Ducati went to a lower frequency on some models due to bearing failures.  I don't think Ducati uses 140 for anything at this point.

That's interesting ....

I went to a track day last friday, my first real ride for this year. The first 2 stints I rode the m800, and after getting used to all the normal noises, I thought I heard one I did not recognize ... If i reved the motor at standstill, I thought there was like a WZZzzzzz.... noise when the revs went down again.
I took off the covers to se if everything seemed OK, which it did, but on the still-warm motor, the belts were quite tight.    

When I got home, I did some checking and experimenting with the modified sleeve,  now 2.5 mm wall thickness:

20210518_103706 by torbjörn bergström, on Flickr

It actually is possible to get very different levels of tension on the belt, "tight" can be very differently tight, but snugging up the tensioner against the sleeve, slightly tightening the fulcreum bolt, the using a small hammer and a drift on the movable tensioner bracket to tighten the belt, there is now a slight gap between the fixed roller and the belt with the sleeve removed.
With the Gates app, that translated to somewhere in the 140 Hz range. Measured with the allen key method, that's tight om the 4 mm ky recommended by Kämna at tthe service course I went to many years ago.  

Doing the same procedure again, but sligtly less tight, gave reasonably consistent readings in the 120 Hz range (with occasional readings of 270 Hz, 55 Hz etc, etc, ....), so that's where I left it for now. Depending on if I hear something or not on the next ride, I might either try even looser belt, or change the bearings (which all felt fine, no rough spots or noice). If there's a noice, I'll probably change the bearings anyway.  

[koko64]

Interesting. There is a certain bearing whine sound that a hot motor can give that will tell you to double check belt tension.

[DuciD03]

... I'm learning some new stuff here ... didn't think belt tension could affect timing / performance so much; then again the professional tune I got done had a noticeable improvement in performance.

[greenmonster]

Rechecked new belts after about 750 kms.
Belts look good, no hints of wear. Belt tension on warm engine same as cold,
new belts have stretched a bit? Only checked w Allen & feeler.
Belts w correct (well... ) tension gives engine bit snappier and easier to start than before.
So the 1/4mm or around 100 Hz method seems right IMHO.

[koko64]