From the beginning of a modern Ducati ownership, there are two things which always come into mind during service; valve clearances and belt's. Clearances are a straight-forward, easy process, but belt tension seems to mistily most who have attempted it. Unlike clearances, which require to have a tool which is very cheap, belt tensioning tools are costly and avoiding there cost is what us home service guys are all about!
I did my first belt change in May 2007 using the advice of a well-known industry tech. Since then, the no-tools necessary approach to belt tension has been constantly on my mind. I decided to put the different methods to the test and prove which ones work the best.
The belts will be first set by the correct method and then every other method is tested against proper belt tension to see if they fall "within spec".
This is the proper way to adjust belts without buying the Clavis Model 4/5 or Gates Model 507.
- Computer (MAC or PC)
- Tuning software (shareware)
- Microphone (borrow from friend)
Once the belts have been installed, you can place the microphone between the two belt pulleys (tension and fixed). I put it on the bottom because the mic was so sensitive it would pick up plucking from either belt. When plucking the belt, the computer software will show the appropriate frequency. Adjust the tensioner to the spec below and your done.
75hz for vertical
85hz for horizontal
A perfect tensioning of the belts. A very interesting note; the 75hz was such a fine-tune adjustment, it took almost 10 minutes to get it and have it stay at 75hz. Using the other methods your going to read about below, it would be 99.5% impossible to get even close to 75hz. The 85hz was much easier and of course the 240hz you could almost do by ear. (240hz is what you use when adjusting for cam timing on testastretta's)
The first alternative method is what I refer to as the "Push to Casing" method. In this, you'll be pushing the belt up, between the two cam pulleys until it reaches the top of the casing OR where the cover rests.
As you can clearly see, the belt almost reaches the top of the case. In the video it does, but under heavy pressure. This method DOES work, but obviously not nearly as accurate as the frequency method.
This is an odd-ball method because its not so accurate, but does require a tool. The caliper measuring method, says the belt should't move MORE then 5mm up and 5mm down in between the two main cam pulleys. So you take a set of calipers, open it up to 10mm and push up/down on the belts.
Yet again, you can clearly see, the belt does ride between the caliper opening. This particular measuring technique "could" work pretty well, but never the less, not perfect under any circumstances.
The second alternative method is what most people call the twist. This is where you grab the belt between the belt drive shaft and the pulleys and twist. You're somehow suppose to tell its a 45 degree twist.
Looks like 45 degrees to me, or is it? This method is flawed because, as in the case push-up method, there isn't any easy way to tell if it can be twisted more or less. Somebody might be able to twist more then I can, so its pretty useless.
Here is a video of the tests so you can see for your self in moving images; Click here to play in WMV
From adjusting my belts for the last 7 months, using method 2 and method 3, I've never had a broken belt or anything go wrong (besides a blown motor, non-belt related) My belts at 6k (1k of track riding) looked brand new when I removed them from the broken motor. Belt tension was set pretty darn well for guessing. But, after the testing above, you can clearly see, the cheap/free method of using a tuning device is super easy and worth the trouble. All the other 3 methods were guess work and unless I had already properly setup tension, you can see how the other methods could have been deceiving. What I've learned in this test is pretty straight-forward. The difference between 75hz and 85hz can't be measured by hand, using your fingers to twist or push the belt. So if Ducati has such a specific frequency for belt tension, there is evidently a reason behind it and EVERY SINGLE service manual I've read, clearly says this measurement is crucial!
So to answer several people's questions on the matter. No, you don't need the special Clavis or Gates measuring tool. Yes, you should use method one, which uses a computer and software to properly adjust your belt tension, especially on a testastretta.
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