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Discussion Starter #1
Does anyone have a link to a timing belt adjustment (tension)? A step by step with pictures would be very helpful.

Thanks in advance...
 

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Believe the belt tension is adjusted based on the vibration frequency so you'll need a tool to measure that. Sorry, that's all I can offer.
 

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I gotta ask...is this how the dealer does it? Do they have a freq. measuring tool they use or do they do it by feel or with a gauge tool?
 

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If you follow that procedure you will not be on the Spec for the DS motor. It is true that the adjustment is now based on measuring the vibrational frequency, with an infrared sensor, and yes any good dealer with a ducati tech has one.

The DS motors have tighter belt tension than the previous 2Vs. Even a 3-mm hex key won't pass easily between the belt and idler pulley when the tension is properly adjusted.

I got set up inexpensively to measure the vibrational frequency with an audible signal. Not as good as the IR but it can work - I had the dealer check the adjustment after I did it and it was spot on.

http://www.ducati.ms/forums/showthread.php?t=19641&highlight=adjusted+belts
 

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I dropped my bike off for the 600 mile service today. I did have a look at the belts a few days ago and I could definitely get the 5MM allen wrench between the belt and the tensioner on both cylinders. I will check what they are like when I get it back.
 

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StraDuc said:
I dropped my bike off for the 600 mile service today. I did have a look at the belts a few days ago and I could definitely get the 5MM allen wrench between the belt and the tensioner on both cylinders. I will check what they are like when I get it back.
Please do that...get back to us. LT Snyder's manual says to tighten until you can just twist the belt 45 degrees in the center of the run. I haven't tried this yet, btw, as my bike is now at 1700 miles.
 

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StraDuc said:
I dropped my bike off for the 600 mile service today. I did have a look at the belts a few days ago and I could definitely get the 5MM allen wrench between the belt and the tensioner on both cylinders. I will check what they are like when I get it back.
If you didn't already discuss it with them, you might want to phone and make sure that they intend to check the belts. Even though it is on the list, some dealers skip it at the first service. Mine would have, if I hadn't requested otherwise.
 

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140 hertz should be the D string on a guitar (the 4th one from the top). I believe that's a D3 (146.83 hertz). So if you have a guitar nearby you can tune the belt just like you'd tune a guitar. Just pluck the belt and pluck the string. adjust the belt until they ring together.

I've never tried it but it be interesting to give it a shot.

-ducadent
 

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Discussion Starter #11
Thanks for all the posts! i went ahead and used the 2-3 mm hex/feel trick to adjust the belts. I just had my belts adjusted not too long ago on my GT and I have Speedymoto belt covers so I just kept comparing my adjustment to the adjustment completed on the GT. I think I will try the 140hz technique in the future but for now this will suffice. The vertical belt on the PS was quite loose so I am certain that my current adjustment is far better than waht it was before. As long as you keep checking your belts for premature wear, defects, etc...you should be able to prevent any potential mishap.

would love to hear any thoughts on this.
 

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Use the Tool, Luke



First of all let me say, it's critical that the cam belts be replaced every 12,000 miles. Space limitations on motorcycles require the use of smaller diameter pulleys that cause the belt to flex more than large pulleys used in automobile engines. Further, Ducati uses a small diameter back-side belt-tensioning idler pulley arrangement that causes the belt to flex in the opposite direction on each revolution. This design approach results in an even greater angle of belt flexing requiring the use of a stronger reinforcement fiber to prevent fatigue failure. The original drive belt design often failed before the first 12,000 mile replacement interval so Ducati switched to a Kevlar fiber reinforced belt.

It’s also important to inspect the idler pulley bearings at each change and also a good idea to replace the belt tensioner locknuts.

Second, Ducati tells us that the proper belt tension is critical to avoid over-tensioning the belts that can lead to premature failure. No one argues with this.

I think it’s interesting to note that the Ducati tool for checking the belt tension on the 4V motors has changed for the testastretta. The testastretta engines, as well as all new dual spark engines, use a harmonic tester that can only be used with the Mathesis diagnostic tool. Also, Ducati now specifies different tension specs for the vertical and horizontal cylinders.

The main reason for tensioning in the first place is to prevent the drive belt from jumping a tooth or walking off it’s pulleys. I would think that the minimum tension to prevent this is well below Ducat’s specs. So why are they so picky about it?

One reason is that it affects valve timing by a couple of degrees. The looser the belt, the more advanced the timing.

My guess, for what its worth, is that they can’t control the manufacturing specs close enough on their supplier’s belts. The suppliers are able to supply belts with adequate tensile strength and at the dimensional tolerances needed, but there’s probably a significant variation between suppliers and production lots regarding belt stiffness.

So you just stretch a less-stiff belt a little more to get the proper tension, you say? Well, yes and no. In terms of linear stiffness, yes - it makes little difference. But in terms of bending stiffness, it changes the way the belt vibrates between pulleys, and in particular, the frequency that it vibrates at. It certainly changes the natural frequency of the belt so as to resonate at different engine rpm. The different specs for the horizontal and vertical cylinder belts is the clue here.

So what? I think that Ducati has traced belt fatigue failures to this phenomena, so they’re trying to control the belts harmonic vibrations instead of just tension.

Of course, it’s still possible to cause belt failure by overtensioning it.

One point bears mentioning here. There’s been a lot written about how to accurately set belt tension. No matter what method you use, what's critically important with any toothed belt is the need to rotate the crankshaft (and the belt) after you set the tension, to assure that the specified tension is the same everywhere along the belt, not just in the part of the belt where you first placed the tension gauge.

If you service Ducati 4V motors for a living, you have set the tension in the belts enough times using the required tension tool and procedure to have become pretty well calibrated yourself as to how tight is tight. So an experienced technician may indeed feel it’s a waste of time. They remember how much the belt will deflect between pulleys when under maximum tension when the engine is hot - and how the same belt feels when everything is cooled down. In other words, they have a “feel” for the spec when they double-check using their calibrated push and pull on the belt.

The rest of us need the tool.
 

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Discussion Starter #13
Shazaam said:



The different specs for the horizontal and vertical cylinder belts is the clue here.
I thought on the DS 1000 both the vertical and horizontal were at 140hz?

I wonder about the whole harmonic technique, I am certain that the technique varies from shop to shop and therefore results in different values. The question is how much different is a value of 150hz than a value of 140hz?

It would be interesting to do a study to look at the confidence interval for multiple ducati service centers.
 

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Well I got the S1K back yesterday from the 600 mile check up. Had to go straight to work after picking it up, so this morning was my first chance to check the belts. The service manager told me, as suggested by YellowDuck, that they just skipped the belt tension--but they only charged me 1 hour labor for the 600 mile service. The only reason for going in for dealer service was to keep the warranty valid anyway, so the low cost was nice- I will learn to do whatever service is really necessary when necessary. I pulled the covers a few minutes ago and found the front cylinder belt is quite tight compaired to the rear-- 4mm clearance at the idler pulley rear verses a tight 2 mm on the front when cold. I guess I will need to find a way to get them done up right. Since I own a music store and have various types of guitar tuners, microphones and an oscilliscope available to me, I will see if I can find a way to measure the 140Hz resonance the belt is supposed to have. I did try plucking the belt and I really can not hear any audible frequency coming from the belt. But then I am used to listening to high quality guitars vibrate not rubber belts. On another note, they also installed my Termi 2 into 1 exhaust--baffles out-- and it absolutely ROCKS!! What a sound! It seems to run better as well, but I really need to ride somewhere besides across town in traffic to tell for sure.
 

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Hey Shazaam-- You say "One point bears mentioning here. There’s been a lot written about how to accurately set belt tension. No matter what method you use, what's critically important with any toothed belt is the need to rotate the crankshaft (and the belt) after you set the tension, to assure that the specified tension is the same everywhere along the belt, not just in the part of the belt where you first placed the tension gauge."

Are you saying we should be checking the belt in positions other than at TDC on the power stroke? I am not trying to be antogonistic- this is my first experience with a belt drive set up and I just want to learn proper technique and avoid a piston and rod that looks like that picture you posted.
 

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StraDuc said:
I did try plucking the belt and I really can not hear any audible frequency coming from the belt.
On the loose one you probably couldn't. On the tight one you should be able to. I found that when I tightened and loosened the tensioner, I could hear the pitch change.

I *really* like the idea of just tuning it by ear. Perhaps more convenient than a guitar would be an electronic tuning fork, or simply a freeware tone generator on the laptop. Just let it run at 140 Hz and tune the belt until it is on that frequency. I bet it would work great!

Edit: I just played with my tone generator a little, and I think you would have to be pretty tone deaf to miss the difference between 140 and 145 Hz. The difference is approximately a semi-tone. The "by ear" method should be pretty darned accurate.
 

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YellowDuck said:
Perhaps more convenient than a guitar would be an electronic tuning fork, or simply a freeware tone generator on the laptop. Just let it run at 140 Hz and tune the belt until it is on that frequency. I bet it would work great!
You guys continue to impress me with your knowledge of all the wonderfulness the 21st Century brings..... "freeware tone generator" on a laptop, indeed. :)
 

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BobHancock said:
You guys continue to impress me with your knowledge of all the wonderfulness the 21st Century brings..... "freeware tone generator" on a laptop, indeed. :)
Okay, but I am picturing ducadent sitting cross-legged on his garage floor before his bike, replete with its sophisticated electronic ignition, to-the-micron-accurate desmo valve train, and 400-pt electronic fuelling map. He reads the section in the service manual about how to assemble and position the $5000 Mathesis kit to check the belt tension, takes a long drag on his cigarette, then reaches for his grandpa's battered old banjo...

*doing*

plucks belt..

*dmph*

banjo - *doing*

belt - *dmph*

He lazily makes a quick adjustment to the tensioner, then leans way down so his ear is right next to the belt..

*doink*

Perfect. All done. He tears the page out of the manual and uses it to roll another dube.

Take THAT ducati.
 

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Oh, I've definately used a banjo and much worse.

For the record, I was using the 5mm-pass-with-heavy-effort-6mm-not-pass-Allen-key method before I read this thread. I saw a video somewhere on the web a while back explainign this method. I tried the doobie method, but I couldn't get the doobie between the idler and the belt.

I did go back and pluck the belt in a few places to check and I can definately hear that it's somewhere around a D... though it's clear that it's a little flat. I could put a mic on it and record it in pro-tools (music recording software) to check the pitch, but i'm pretty good with just my ear. So at least in my case the allen key method is yielding similar results.

It's probably closer to tuning a piano than a guitar. Actually imagine tuning a casio that is running though a Rat distortion pedal. the note is more percussive than ringing. It decays really quickly and it's got a lot of hair on it so it's tough to pick out the note.

If you want to go really cheap, you might be able to use a cheap guitar tuner ($20) with a cheap radio shack mic plugged into it instead of a guitar cable. Just be aware that the meter is going to bounce like crazy, settle for one second and then decay.

-Ducadent
 

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you can actually do the following...play a tone with the tone generator and capture it with the virtins sound card tool. You can see how it closely matches the frequency generated....yes....I am bored :sleep:
 
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