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Author Topic: 2V belt tension question (!!)  (Read 25049 times)
howie
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« Reply #30 on: June 11, 2009, 08:03:22 PM »

How tight should the Allen key fit between the belt and roller? Should I not be able to get the next size in there?

Until you develop the correct feel make sure a 4 mm. allen goes through real easy and a 6 mm is real tight.  You should now have a light drag with a 5 mm.  As Scott said, better to err on the side of loose.
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AndrewNS
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« Reply #31 on: June 12, 2009, 01:12:58 AM »

I understand exactly what woodyracing is saying, and it would be the real deal...probably the only way to get consistent audio readings between the two belts as well. It would probably give the best results even when using the allen key method 'cause the cam timing would set correctly after each adjustment, and that would be going off as the belts stretch in normal use. But it is a bit of a ITA, especially for someone like me who lacks the correct tools to lock everything in place. Not meaning to derail this thread, but how much do the locking tools cost? Could you make some?

Not like I think you'd get much return on this, but I sorta like the thought of doing things precisely when I can (within reason).
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howie
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« Reply #32 on: June 12, 2009, 05:22:32 AM »

The correct tool can be made from a screw.  I don't remember the size.  The rubber piece behind the cam pulley has a screw in it.  Remove this screw and get one long enough to do the job.
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scott_araujo
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« Reply #33 on: June 12, 2009, 06:04:12 AM »

Not like I think you'd get much return on this, but I sorta like the thought of doing things precisely when I can (within reason).

So you set it precisely then start the engine and get different parts of it to somewhere between 200 and 1000 degrees.  The belts get hot too.  They stretch, they settle, they're not perfect so they are just a bit tighter at one spot in their rotation than in another.  Of course there's the whole debate as to whether the vertical runs a little hotter since it's out of the air stream.  Did you set them differently or the same?  Some people set them the same some set the vertical a little looser and no one seems to have problems.  Then you ride, turn it off, and let it cool.  You do this between dozens and hundreds of times over the next little while until you change the belts again.  Most people don't check the belts between changes and they certainly don't both stretch or settle in the same, yet again, no one really seems to have any problems.

I'm not trying to be a jerk here at all or criticize.  Good maintenance is a good thing.  What I'm saying is that it's not rocket science, it's not all that critical.  Setting your belts to proper tension is a good thing but there is an acceptable range and it's fairly easy to hit.  The usual stress and vast temperature swings of an air cooled engine just running will play havoc with your settings immediately.  It probably matters more for 4V bikes with higher tension and tighter tolerances.  For a 2V just make sure they are not too tight so you don't stress the seals and bearings.

Also, you can do this and much more Smiley  Ducati maintenance is not that hard.  Doing your own work can be one of the most satisfying parts of owning any motorcycle.

Scott
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AndrewNS
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« Reply #34 on: June 12, 2009, 08:24:35 AM »

I certainly agree with you about people making way too much out of all this "belt tension" stuff - it's sort of like a Ducati-specific version of the oil threads that run endlessly on other boards laughingdp.

On the other hand though, those belts do stretch, and when they do the slack is taken up by a movable tension roller on one side. Just trying to visualize this in my mind's eye, if you had 1/4 inch of belt stretch (which seem reasonable) and it resulted in that much motion around the cam pulleys from a reference position I'm guessing that would be what, maybe 5 - 10 degrees of rotation?

I don't know if that's enough to make a noticeable difference in the way a bike would run, but it seems like it should. Just thinking out loud here - anyone can feel free to correct me if I'm wrong.....I should duck now...     
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Speeddog
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« Reply #35 on: June 12, 2009, 09:05:30 AM »

1/4" of belt stretch would be *huge*.
That would be 1/8" per 'run'.
4-valve pulleys are 18 tooth, 8mm pitch IIRC.
So that would be about 8 degrees of change in cam timing.
That would cause a noticeable change in how the bike ran.

scott_araujo pretty much summarized it in his last post.

The belts are made from some variety of rubber with kevlar 'string' to carry the load.
The kevlar isn't going to stretch much at all.
The teeth will compress and take a set over time, due to the heat and load.
And they'll wear down a bit, that's where the rubber 'dust' you see inside the belt covers comes from.
So, that's where the slack will come from.
I've seem 'em gain about 2mm of clearance over 5000 miles or so, meaning that belts set to 5mm at the tensioner end up at 7mm.

I haven't seen any outright belt failures.
I've seen a couple of belts very close to failure from seized tensioner rollers.
 
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scott_araujo
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« Reply #36 on: June 12, 2009, 09:41:11 AM »

My first set of belts stretched A LOT.  I put them on at proper tension and rode 1400 miles to get home.  When I checked them on arriving they were WAY loose, not skipping a tooth but close.  This second set hasn't stretched so far but it's only been a few hundred miles.  Now I check them every few hundred miles after a new install until they settle, then at every oil change.  It only takes a few minutes, 10 seconds if you leave the covers off.  As mentioned, checking that the rollers aren't frozen is just as important if not more so.

Scott
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ollie
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« Reply #37 on: March 25, 2011, 08:00:26 PM »

Bringing this one back from the dead.

My belts are due for replacement, it's been about 2.5 years sinece they were done last, by the last owner.
 I pulled the covers off to take a look at the condition of them and noticed they are way loose. Was expecting the tension to be around the  the 5mm allen key mark, but at the moment I can fit a finger through, if I try hard enough I could possibly slip the belt off the tensioner wheel!!!

Bike has been running fine, with no noticible issues. What should I do?
 - Tension them  up myself before I start it again- I've never done this before but have watched the vid on you tube and It seems easy enough
 - just ride the bike to the mechanic and get the belts changed - bit nervous now after seeing how loose they are.


Obviously, these are way, way out of spec - could this have caused any issues I should be aware of, or with timing belts it's either Ok or really really bad, with no inbetweens??
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ducpainter
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« Reply #38 on: March 25, 2011, 08:05:48 PM »

Bringing this one back from the dead.

My belts are due for replacement, it's been about 2.5 years sinece they were done last, by the last owner.
 I pulled the covers off to take a look at the condition of them and noticed they are way loose. Was expecting the tension to be around the  the 5mm allen key mark, but at the moment I can fit a finger through, if I try hard enough I could possibly slip the belt off the tensioner wheel!!!

Bike has been running fine, with no noticible issues. What should I do?
 - Tension them  up myself before I start it again- I've never done this before but have watched the vid on you tube and It seems easy enough
 - just ride the bike to the mechanic and get the belts changed - bit nervous now after seeing how loose they are.


Obviously, these are way, way out of spec - could this have caused any issues I should be aware of, or with timing belts it's either Ok or really really bad, with no inbetweens??

You could adjust them and then take it to the mechanic.

If nothing bad has happened yet then no damage has been done. It is really...really bad when it goes wrong.
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ollie
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« Reply #39 on: March 25, 2011, 08:13:31 PM »

Thats a relief, I'll have a go a tensioning them before taking it in to get new belts

How could they have got so loose - new belts were last done at the local dealership. I wouldn't have expected belt wear to be this much, especially seeing as though the km's are still below change over specs.

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Speeddog
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« Reply #40 on: March 25, 2011, 09:02:04 PM »

Bringing this one back from the dead.

My belts are due for replacement, it's been about 2.5 years sinece they were done last, by the last owner.

~~~SNIP~~~

Do you have a service receipt showing a belt change or was it just what the last owner *said*?

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speedknot
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« Reply #41 on: March 25, 2011, 10:08:10 PM »

WTF?  Using a frequency analyzer to adjust belts?  I thought the Germans liked to over engineer their shit.  Like some have said, go for feel or the 5mm allen method. 
While at the dealer someone mentioned that they use a tuning fork to adjust the valves.  Is this true?  What ever happened to two wrenches and a feeler gauge?  I'm freakin lost!
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ollie
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« Reply #42 on: March 25, 2011, 10:23:50 PM »

Do you have a service receipt showing a belt change or was it just what the last owner *said*?



yup, got a service receipt for the replacement of the belts - there is a note the bottom that indicates that the first set of belts that were replaced were too tight  Roll Eyes
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ducpainter
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« Reply #43 on: March 26, 2011, 10:33:19 AM »

WTF?  Using a frequency analyzer to adjust belts?  I thought the Germans liked to over engineer their shit.  Like some have said, go for feel or the 5mm allen method. 
While at the dealer someone mentioned that they use a tuning fork to adjust the valves.  Is this true?  What ever happened to two wrenches and a feeler gauge?  I'm freakin lost!
The 5mm wrench method doesn't work for the DS or 4V.

I guess the 450 twist method can be used if you have a feel for it.
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chris1044
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« Reply #44 on: March 27, 2011, 04:27:25 PM »

WTF?  Using a frequency analyzer to adjust belts?  I thought the Germans liked to over engineer their shit. 

At least the Germans engineer their shit...from all the posts I've read on this topic, it sounds like Ducati Engineering forgot that the timing belts load the cam bearings when the engine is spinning, and under-engineered them.  That's why they have this fancy tuning method.

On a moto-GP bike, OK, fine.  But on a bike that's going to be sold to the masses and not serviced/done by a DIY?Huh?   laughingdp Someone surely got a promotion for this....
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