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Discussion Starter #1
I live way too far from the nearest Ducati service center, so have to change them myself, on my 2015 Icon. I've heard it's an easy job, but really don't want to screw it up given the how serious a failed timing belt can be to my engine / my very life. To be clear, I'm a real rookie when it comes to working on my bike, so don't know how good is good enough when it comes to trying to install these to spec. My original belts looked great after removing them, even though I rode them hard, well past their recommended mileage, so I'm thinking they were set by the factory pretty well.

Brand new OEM belts are on, and have found several different routes people have suggested for tensioning them without the Ducati sonic measuring tool specified by the service manual.
Method 1) slide a 5 mm allan key between the belt and mobile tensioner. Should slide through with a wee bit of effort. But the 6 mm should not.

Most vids I've seen recommending this way have been for Monsters, not Scramblers, and the recommended belt tensions are different. 110 hz for the Monster and 140 hz for the Scrambler. Does that mean it should be tightened more for the scrambler? Like to the point of where the 5 mm doesn't slide through? And do you do this slide-test through both tensioners for each belt? No vid or written explanation I've found specifies either way, but I assume that you would.

Method 2) Download a guitar tuning app and use it in the same manner as the Ducati sonic measuring tool. Tried this too, and the problem here is a) it seems very inconsistent. I got readings all over the place, while testing in quite environment (when I got readings at all). Used numerous different apps hoping for one to have repeatable, consistent readings. Even better if a few of the apps gave the same reading. Didn't happen. Also, should you test both sides of each belt? Same issue as above. I only have seen them testing one side of the belt, but assume you'd need to test both.

Is the tension the same by the way for both the horizontal belt and vertical belt? Just about every vid I saw had people recommend a slightly different tension for the vertical belt, as that area tends to run hotter than the horizontal belt/cylinder as it gets more air. The service manual only recommends one tension.

One other point of confusion I had while using these two different methods was that if I did get a reading on the guitar tuning app that looked to be around 140 hz across a few tests, that particular tension was way too tight to pass through 5 mm allen key between the belt and mobile tensioner. If the 5 mm key passes through ok, the belt frequency, where tests yielded a few repeated results, was way too low.

Any easy, reliable methods you all use? I'm chomping at the bit to get back on the road to enjoy the last decent riding days we have left. And thanks if you managed to read through this whole thing.
 

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Discussion Starter #3
Yes thank you for the link. It has a clear explanation and very useful pictures.

But answers none of the questions I asked above. I have no Ducati Harmonic Belt tool, no access to one, and not going to pay 645 plus shipping for the one on ebay.

My questions all regard tensioning the belt correctly WITHOUT the tool specified in the link. Before I'm told to use the 5 mm allen wrench method, or download a guitar tuning app, please read above if you have time (it's long, I know :ambivalence:)
 

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I used a tuning app. Both belts are 140 as the instructions state but close is good enough. Go throu the link I gave you it's a step by step. The other bikes have a lower tension spec so don't go by the allen wrench method. It's an easy job just take your time.
 

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Discussion Starter #5
I used a tuning app. Both belts are 140 as the instructions state but close is good enough. Go throu the link I gave you it's a step by step. The other bikes have a lower tension spec so don't go by the allen wrench method. It's an easy job just take your time.
Thanks, yeah I've gone through all the steps up to the tensioning part, as mentioned. And as you stated, the specified tension for the scrambler is tighter than earlier monsters, so wasn't convinced the 5 mm allen key trick would work here.

Which app did you use, and did you tension both sides of the belt? As you can see in the pics in the link posted, they only have a circle around one side of the belt, but it seems to me the tensioning should be done for both sides (ie both sections of the same belt between the TWO mobile tensioners and the belt roller), because frankly, the other side of the belt could be anywhere in terms of its tension, if not also tensioned properly.
 

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I used universal tuner. Yes only measure the one part of the belt for tension. There are 2 belts. They are exactly the same. I did the horizontal belt first because it was easier and then counted the teeth on the belt to match the verticle belt.
 

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Discussion Starter #9 (Edited)
Please explain? You can’t adjust both sides independently right? It’s the same belt...
Yeah, that's what I figured having read / seen the various explanations.

But the belts have teeth, and so do the pulleys / belt roller. And it takes some effort to overcome the weight and resistance behind the belt roller even though I have the rear wheel elevated and have removed the spark plugs.. So the belt doesn't "slide freely" / or turn the pulley during adjustment of tension, not allowing the same tension to be transferred uniformly. Therefore the tension on one side of the belt is independent of the tension of the other side of the belt. I'm not just guessing this. I could clearly see that the pulley didn't budge, and that one side of the belt had a different amount of tension than the other. Then I tested using the 5 mm allen key method. I could have the tension completely off (way too loose or waaay too tight) and one side, but still get the correct test results on the other side using the 5 mm allen key slide through method (or the tuning app method for that matter). Didn't matter what the tension was on the "untested side", it didn't have any bearing on the tension test results of the tested side. That seems to me like a not very accurately tensioned belt.

But if the pulleys / rollers did turn freely during the process, I could see issues there too. 1) It would mean that your reference markers on the pulleys would no longer match up with the reference markers on the case as you adjusted the tension, no? At least a bit. And 2 ) If you finally zero in the vertical belt, and the pulleys / belt roller moved freely, wouldn't the adjusting of the horizontal belt change the alignment of the reference markers on the vertical belt, as a turning roller would effect both belts? At least a bit? This is just me guessing whwt could happen. But to make it clear again, the rollers and pulleys did not budge as I tensioned my belts, regardless of how tight/loose they got while fiddling around. And again I wonder if they should have despite my maybe uninformed musings above.

I realize most people sound like they slap them on and kind of close is good enough. Or a quick "quarter turn of the belt" test, and off they go. Great, all the power to them. I'm a total rookie, but I'm wondering, if I wanted to do it as well as I could, given the tools that I have, how could I do that? I push my bike pretty hard, and ride a lot, and want the piece of mind that I did the job right. And until I get way more experience working on my bike, I won't really know which specs have what amounts of freeplay or over specification.
 

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OK - when you say the rollers and pulleys did not budge - what do you mean.. rotate?

I have not done them on a bike but have done plenty of cars.

With the engine timing marks aligned - note the exact position of the tensioners (exact - with photos - marks - measurements- I think in the Scrambler - you can measure the distance between the tensioner pulley and idler pulley with a vernier caliper - slacken the tensioner.

Remove the old belt (belts)

Check ALL bearings / tensioners and pulleys for play and wear and the tensioner and idler bearing for free rotation without noise / play.

Double check the alignment marks are revalid.

Fit the belts and tension the tensioner to the same exact position they were before you started... this was the position for new belts from factory.

Recheck all alignment marks.

Recheck the belt tension looks correct (approx)

Turn the engine over by rotating rear wheel - in gear.. two or 4 whole revolutions of the engine and bring marks back in line... - TURN in the direction the engine rotates under power... this is important so the slack is in the correct place...

Now the belts have had chance to seat and tension sort itself out.

Now for a car - I would just check tension as per recommendation - movement / turn etc.. with X pressure... or with a gauge.

On the Ducati... now do the testing using the app and strumming the belt at the specified spot and with phone mike near belt.

You will have different tensions in different places on the belt... that is a fact.... so it is important to just check and verify at the specified spot..

Adjust tension if necessary...

Repeat the above turn and check if you adjust the tension until you do not need to adjust either belt..

Then check the timing marks again...

Refit all covers etc... you should be done.
 

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Yes, Ducati does use two belts.
I’ve done many, many belts over the years using all the new gizmos invented along the way. Each time a new fangled method or over engineered way comes along the belts still end up turning 90 degrees on the longest run with finger and thumb pressure.
I’m not joking, all the manufactures think they’re ahead of the game and cutting edge. Ma-hole.
 

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Discussion Starter #13
Yes, Ducati does use two belts.
I’ve done many, many belts over the years using all the new gizmos invented along the way. Each time a new fangled method or over engineered way comes along the belts still end up turning 90 degrees on the longest run with finger and thumb pressure.
I’m not joking, all the manufactures think they’re ahead of the game and cutting edge. Ma-hole.
Haha well said. I'd just be happy if any 2 methods I tried gave me similar results.
 

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Discussion Starter #14
Gusan, if you are like me, you will be relieved to know that you are probably overthinking this one. My husband and I used this guide:

Ducati Suite- Belt Tension Adjustment

Take a look here and scroll down to Derek's post from Aug 9th, 2016:

https://www.scramblerforum.com/threads/valve-adjustment.4901/page-3

Reassuring to know that you are completely on track, but it's not that terribly critical. You'll have that bike back together in no time.

Sarah
I know, for sure I'm being a little to exacting about this haha. But I just can't help wondering what is the best way, especially if that way may take no more time than the other ways being used/recommended. The belts I removed from my bike were used way past their recommended mileage, and I push my bike very hard. So I'm thinking the factory set them up pretty well and would like to get mine likewise well sorted.
 

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Discussion Starter #15
OK - when you say the rollers and pulleys did not budge - what do you mean.. rotate?

I have not done them on a bike but have done plenty of cars.

With the engine timing marks aligned - note the exact position of the tensioners (exact - with photos - marks - measurements- I think in the Scrambler - you can measure the distance between the tensioner pulley and idler pulley with a vernier caliper - slacken the tensioner.

Remove the old belt (belts)

Check ALL bearings / tensioners and pulleys for play and wear and the tensioner and idler bearing for free rotation without noise / play.

Double check the alignment marks are revalid.

Fit the belts and tension the tensioner to the same exact position they were before you started... this was the position for new belts from factory.

Recheck all alignment marks.

Recheck the belt tension looks correct (approx)

Turn the engine over by rotating rear wheel - in gear.. two or 4 whole revolutions of the engine and bring marks back in line... - TURN in the direction the engine rotates under power... this is important so the slack is in the correct place...

Now the belts have had chance to seat and tension sort itself out.

Now for a car - I would just check tension as per recommendation - movement / turn etc.. with X pressure... or with a gauge.

On the Ducati... now do the testing using the app and strumming the belt at the specified spot and with phone mike near belt.

You will have different tensions in different places on the belt... that is a fact.... so it is important to just check and verify at the specified spot..

Adjust tension if necessary...

Repeat the above turn and check if you adjust the tension until you do not need to adjust either belt..

Then check the timing marks again...

Refit all covers etc... you should be done.

Thanks, a lot of good info here. And yes, when I say don't budge, I mean don't rotate (could they be expected to budge any other way?)

But again I need to ask, do you test both sides of the belt (ie at or between both tensionsers, depending on the testing method?) As I stated here a few times, it's pretty obvious that testing one side of the belt isn't telling you what the tension is on the other because the teeth/resistance of the pulleys don't allow the tension to be uniform, as you tension one tensioner or the other. Am I wrong about this? If so, why?
 

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You never get even tension on a belt... one side is in tension and the other side not


The guide that was published earlier showed where to test the frequency...

Same on your chain - one side is tension the other is slack... but with a chain you check the slack side - not the tension side.
 

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Discussion Starter #18
You never get even tension on a belt... one side is in tension and the other side not


The guide that was published earlier showed where to test the frequency...

Same on your chain - one side is tension the other is slack... but with a chain you check the slack side - not the tension side.
OK I see what you're saying. Kind of. But I'm still a little confused as I wonder wouldn't it matter if the other side was waaay to tight, or waaay too loose? It seems either situation is possible while checking the tension on one side only. Wouldn't it be an OK idea to look a both sides so that the overall tension is somewhat understood?
 

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The engine (crankshaft) is pullling the cam shaft around - on a traditional engine - there is variable tension on the belts as the valves open and close - caused by the springs and the gaps between springs starting to compress.

The Ducati Engine does not use springs.. to close the valves - the camshaft pushes and pulls the valves closed.

So in Ducati the variability of tension on the belt is much less than a car or say inline 4 Jap Engine.. but there is still some variability due to no springs.

The slack side has to have some slack so as to allow for thermal expansion on the engine - hot engines have a larger distance between pulleys than a cold engine and not be too tight.. to overload the bearings during this expansion

The slack side therefore acts to control the expansion and wear that occurs on the belts... some engines used to (and probably still do) use springs to control the tension...

But as others have said its not that important.. too slack and it risks jumping a tooth or near jumping a tooth that will cause wear / damage

Too tight will load bearings too much on a hot engine and cause wear on belt and bearings..

But being perfect tension will only happen at one time and one temperature... before belts wear.. or belts engine is hot....

What I am saying is you can set exactly perfect pitch - run the engine for 10 minutes and belts will be warm... you will get a different number...

1 week later on a cold engine after belt has seated in... you will get a different number.
 

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Discussion Starter #20
The engine (crankshaft) is pullling the cam shaft around - on a traditional engine - there is variable tension on the belts as the valves open and close - caused by the springs and the gaps between springs starting to compress.

The Ducati Engine does not use springs.. to close the valves - the camshaft pushes and pulls the valves closed.

So in Ducati the variability of tension on the belt is much less than a car or say inline 4 Jap Engine.. but there is still some variability due to no springs.

The slack side has to have some slack so as to allow for thermal expansion on the engine - hot engines have a larger distance between pulleys than a cold engine and not be too tight.. to overload the bearings during this expansion

The slack side therefore acts to control the expansion and wear that occurs on the belts... some engines used to (and probably still do) use springs to control the tension...

But as others have said its not that important.. too slack and it risks jumping a tooth or near jumping a tooth that will cause wear / damage

Too tight will load bearings too much on a hot engine and cause wear on belt and bearings..

But being perfect tension will only happen at one time and one temperature... before belts wear.. or belts engine is hot....

What I am saying is you can set exactly perfect pitch - run the engine for 10 minutes and belts will be warm... you will get a different number...

1 week later on a cold engine after belt has seated in... you will get a different number.[/QUOTE

I really appreciate the time and effort you are taking to explain this, and I might be slow. but what I'm understanding is: there is no point trying to be precise. Or only being precise with one side of the belt, but not the other, which could have any random tension. Which is really not that precise?
 
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