The Texa arrived today: I was a little worried at first that I'd been sold a dud because I couldn't get a reading from it with a finger click, so with an old used belt I've kept for some reason I built a Mk1 Nasher's adjustable belt tensioning rig: And got some consistent results from it: Better get an order off to Exige for some belts so I can have a proper play.
I have used Continental's software for hertz measurements, and it has been quite successful. Microphone quality is quite important in these situations. In an outdoor environment and using my phone, I struggled a bit, but I think I was able to get a reading in the 135-140 range with Continental. I will double-check to confirm. Fundamentally, it's not much different from tuning an instrument—except instead of aiming for a note, we're trying to capture a specific frequency. The workshop manual specifies a maximum tension of 140+5 for both cylinders. However, when I checked the tension set by the service before removing the old belts, I remember it being in the 120-125 range, which makes me wonder. Because of this, I will set the new belts in the 120-130 range. The workshop manual also specifies 80 for used belts.
So what I mean is, we're trying to make an adjustment with a similar logic, of course, the laser makes a more precise adjustment in this case, as it doesn't incorporate external or ambient noise.
https://ibb.co/fdYPSxc7 I have a question. The frequency value given by the Monster 797's manual (140+5), but generally, it is said to be 110 Hz. What should I set it to
The belts always slacken off once they've been in use for a while. I believe they don't stretch too much, but the teeth also wear to shape allowing the belt to sit lower on the pulley. You set the tension high when new to allow for this. From memory, and somebody please disagree if I'm wrong, the recommended tension to set used belts to is @80Htz if you refit them for any reason. 140 sounds very high to me, but your 797 is a far newer bike than I've worked on.
I agree with you @Nasher - I did some (heavily-filtered!) internet reading on this yesterday. Seems like new (assuming 'official' Ducati) 797 belts are set to ~140Hz!! However, the information also stated that a 'used' belt is one that's been on a running engine for even one short run, with the 'used-belt' setting being 80-85Hz.
I think it would be a good idea for me to do the same, because it has the same block as the Scrambler 800, but the workshop manual mentions a higher tension. The previous old belts installed by the service were around 120. Also, I didn't buy OEM products; I used the Dayco KTB1202HT set, which includes the belt and bearing set, for the new belts.
Thanks Keith_P, glad I'm not the only one that winced at 140Hz, although if they drop to 80Hz very quickly it would be OK. Perhaps setting very tight helps them Wear in and drop to 80Hz quicker. I'm not sure I'd be comfortable with assuming that. My 1000SS and M1000 both have Air-cooled 2/valve motors, although larger and twin spark, but the research I did suggested Very strongly that the 5mm/6mm Allen Key 'Feeler' method I felt so comfortable with on my older 900s was not to be used on the newer bikes. .
Thanks @nelly We all need to remember that the part of the belt being measured is a different length on the 2V than the 4V engines so, along with the potential difference required by that difference, we're comparing apples with pears. Useful image posted a few years ago on Ducati.ms website (I'd treat the stated frequencies as comparisons, not absolute):
