Cam belt tension

[richy]

HI just took the bottom cam belt cover off my 2013 1100 EVO 368 miles and was surprised how slack the cam belt is,are they normally quite slack .On cars that i've had the belts were always under tension.

[slob]

looser than you might think

how to use a guitar tuner app (eg 'Pro Tuner Lite' for iPhone) to check tension as in tpart 2, below
http://www.youtube.com/watch?v=oXUgtytXI9o
http://www.youtube.com/watch?v=ETUD6AfK2d8
I found this quite challenging, so double checked using the tried and tested 'allen key method'
http://www.ducatisuite.com/belttension.html

[utopia]

I've heard about various frequency based methods for checking belt tension, including (I think) the mysterious Mathieson (?) tester, but this is the first time I've seen any of them used.
My ears pricked up when I heard that a guitar tuner could be used, as I have one of those hanging around.
I must say though, having watched the video, my original scepticism was confirmed.
First of all, the method seems very vague, requiring a certain amount of interpretation of a fluctuating readout (even without the extra complication from the 60Hz fluorescent lights).
Secondly, I notice that Chris checked the frequency by twanging both the upper and lower runs of the horizontal belt. If you look at the distance between the drive pulley and both the fixed and moving tensioners, you will notice that they are slightly different. This will surely give different frequency readings for the upper and lower runs. So which one do you use.

Personally, I have a theory that the high-tech testers were introduced simply as a quality control measure designed to eliminate or at least reduce the possibility for operator error.
The mechanical methods, eg allen key, require a certain amount of mechanical "feel", and some mechanics will have lots of this while others may have less, introducing a potential for variation.
By specifying the use of a clever tool, this potential for variation between different mechanics is eliminated.
Trouble is that high tech does not necessarily mean high performance, and in this case I think this is a significant issue.
In short, the frequency method looks totally crap to me, and I will continue to rely on my trusty 5mm allen key, used with care.

While I'm on the subject ....why an allen key anyway ?
Surely a 5mm round bar would be more sensible ?

Actually, when I do my belts I adopt a couple of extra useful strategies.
First, I mark the position of the tensioner backplates (fibre-tip marker) on the engine casing, before loosening anything. This gives me a reference to set the initial tension to when the new belts are fitted, and a reassuring check that my retensioning is in the right ballpark when the job is finished. In fact, when properly tensioned, I find that the marks invariably line up in the same position as for the old belts.
Secondly, once the belts are fitted and tensioned, I go and have a cup of tea and a smoke. Then I return and repeat the tension measurements, having first turned the engine over a couple of times. In an extreme case I might even sleep on it and repeat the tension measurements a third time the next day. The clearing of the mind between tests seems to focus my attention and maximise the degree of "feel", as well as giving extra confidence in the end result.

[Dookbob]

I,ll go with Utopia on all counts.

[Dirty]

The belts need to be at 'day after huge argument' tension. You know that period when everything is beginning to settle down but 1 wrong word could send a heavy object flying at your head. You can normally test this out by suggesting a bit of a romantic interlude. Screaming = too tense, Smile and a wink = too loose, Look that can kill = just right :)

[gary tompkins]

If the belts need adjusting it should be picked up at first minor service interval

At just 368 miles I'm assuming it hasn't had this service yet?

[rollo22]

Give your dealer a call being brand new and still under warranty
Or wait till first service

[richy]

Thanks for the replys.

[BeePee]

There's a video on youtube showing the tension, run a 5mm allen key betweennthe tensioner and belt......you shouldn't be able to run a 6mm key without some force/2 handed

[utopia]

Actually, while you've got the cases off, it might be worth checking the tension properly yourself anyway.
Its a fair assumption that the tension is fine after such low mileage, which means that you'll gain good experience of what a correctly tensioned belt should feel like.
Then when time comes to pay for a belt change, you'll be able to do it yourself with confidence.

Now that I remember it more clearly, the first time I tentatively approached a belt change I went about it like this.
Having set the old belts in the correct position and marked the position of the tensioner pulleys, I measured their tension before removing them.
I did this slowly and carefully a number of times, as I suggested earlier.
I also did it by a number of different methods namely the allen keys, the belt twist, and the general jiggle about.
This not only gave me multiple checks, but also gave me a much better feel for the system as a whole.
I can't stress too highly how important this feel is.
Even the way that you pull the belts off the pulleys for the allen key method makes a difference, because of the way the belts form an angle around the tensioner pulleys. Pressing the belt with a single finger to one side of the pulley gives a different reading to pressing it from the otherside, or indeed pressing it from both sides (the method I use).
And if you impart a slight twist to the belts while pushing, that makes a difference too.
And you need to hold the allen key dead square to the belts, or else .... etc, etc.......
As I said before, I think the main point of the high tech test methods is to eliminate operator error, but actually I reckon that belts set manually can possibly even be more accurate once you have a good feel for the system.
Anyway, then I fitted the new belts and did the same multiple checks (and drank more tea).
My original plan was to then perhaps get the local dealer to check the belt tension, but in the end I was confident enough not to bother.
However, if you have a free service coming up then, if you check yours now, you'll get that bit into the bargain, as it were.

I should say though, I only have personal experience of the old style 2-valve monsters.
I wouldn't think the evo is much different though.

[zhango]

I should say though, I only have personal experience of the old style 2-valve monsters.
I wouldn't think the evo is much different though.
The Allen key method does not give the ideal belt tension of 110Hz on 1000ds engine - the belts will be too loose so I guess this is true for 1100 engine also.

[Capo]

The allen key method, does not confirm that the tension is correct as required by the design, only a frequency (sonic) test can do that.

[Dirty]

How do they test tension at a dealership? Do they have special tools/machines?

[Capo]

Yes authorized dealers must have all necessary special tools, if the manual calls for use of a sonic belt tension gauge then that procedure has to be followed.

[utopia]

The allen key method, does not confirm that the tension is correct as required by the design, only a frequency (sonic) test can do that.

Why not ?
Surely deflection is a function of tension, just as frequency is.

Unless you are saying that the allen key method isn't accurate enough, in which case you may well be right ....I don't know as I haven't seen or done any comparative tests.
Certainly there is more SCOPE for error with the allen keys, but the consequence of this will vary according to the skill of the mechanic.
In fact, in the light of this, maybe I need to do MY OWN comparative tests.
I do have a guitar tuner and I am due a belt change, so I'll give it a go. I suspect I'll find that my equipment is inadequate though. But anyway, it'll be interesting.
Can anyone tell me the correct frequency for a yr2000 M750 ?

[gary tompkins]

The older 2 valve engines don't need/use that method so why bother?

I used to set mine with a fishing spring balance on tension roller. 10lbs pull rings a bell but it's been a while so would need to check manual. Now I just use the twist method mid belt run done by feel. Last six sets of belts I've changed were done this way and it worked fine. Why over complicate a service task for the sake of it?

[utopia]

Yep, I kind of agree.....just curious really.

I also wondered about using a fishing balance, but even that seemed a bit like overkill.