I downloaded the free guitar tuner software and bought a microphone to plug into my laptop, but found the sonic method of checking timing belt tension tedious and frustratingly non-repeatable. Next, I tried the 45-degree twist method, but found I could twist the belt to approximately 45-degrees with moderate effort regardless of how tight or loose I set the tensioner. Finally, I settled on the +/- 5 mm flex method, which I found both measurable and repeatable.
Set with =/- 5 mm flex, my initial impression was the belts felt slightly loose, so I left the covers off, started the bike, and watched the belts for slap. The belts did not slap or flap even when blipping the throttle. Satisfied the belts were not too loose; I went for a ride to warm the engine to normal operating temperature. At the end of the ride, I found the belts had snugged up noticeably with the expansion of the cylinder heads, but still had what I consider a desirable amount of play (~2-3 mm) to preserve bearings. They were not too tight when hot.
Being new to Ducati, this was an interesting exercise. I am comfortable the belts are well within tolerance.
-Jeff
Thanks for the info. Got the same bike and need to do my belts pretty soon. Bought it used and given it's age I'd feel better with fresh belts.
Question, you adjusted the belts without replacement? Was curious if you changed them were you able to get them off the crank pulley without trouble. I've read some DS motors, mostly on Multi's, have some clearance issues with the case that make getting the belts on/off a little tricky.
What started as an inspection of the belts as part of the 600-mile service (performed at 935-miles) became an adjustment because I could not help messing with them to learn. I ended up setting the tensioner about where it was originally indicating the belts had stretched little if at all.
I did not see any reason the belts would not simply slip off and on for replacement. The horizontal cover, on the other hand, requires some finessing.
-Jeff
Quote from: mikeb on April 06, 2010, 05:19:03 AM
Question, you adjusted the belts without replacement? Was curious if you changed them were you able to get them off the crank pulley without trouble. I've read some DS motors, mostly on Multi's, have some clearance issues with the case that make getting the belts on/off a little tricky.
The crank pulley is fairly close to the case so getting the belts on and off takes a little wiggling. Nothing that would damage the belts though.
I just replaced my belts and double checked the tension of the old belts before taking them off. The old belts were set by frequency (110Hz) and checked out at about 3mm with the wrench test. I set the new belts to 3mm as well with just a bit more slack for the vertical cylinder.
Quote from: pennyrobber on April 06, 2010, 07:40:42 AM
checked out at about 3mm with the wrench test.
That sounds about right.
-Jeff
Quote from: pennyrobber on April 06, 2010, 07:40:42 AM
I set the new belts to 3mm as well with just a bit more slack for the vertical cylinder.
Why? I've never heard/read any belt replacement how-to that spec'd a different tension for the vertical cylinder.
I'm also assuming for the wrench test the premise is the same as other 2v motors. Except in this case the 3mm fits and a 4mm won't?
Quote from: mikeb on April 06, 2010, 07:56:44 AM
Why? I've never heard/read any belt replacement how-to that spec'd a different tension for the vertical cylinder.
Some sources feel it is wise to leave the belt on the vertical cylinder a bit looser because the rear cylinder runs hotter and expands more than the horizontal cylinder.
-Jeff
Quote from: jgrm1 on April 06, 2010, 08:03:34 AM
Some sources feel it is wise to leave the belt on the vertical cylinder a bit looser because the rear cylinder runs hotter and expands more than the horizontal cylinder.
-Jeff
Bingo!
Makes sense. After thinking about it I assumed that was why. Just curious why, if that's the case, Ducati didn't simply spec different tension for the vertical.
Good food for thought.....
I wouldn't guess on the belt tension. I found when using a computer, you have to put the microphone at the correct spot, between the pulleys, and fasten it down (I used duct tape) so it dosen't move. I was getting repeatable readings. At 110 hz the belts are pretty tight.
Quote from: jgrm1 on April 06, 2010, 08:03:34 AM
Some sources feel it is wise to leave the belt on the vertical cylinder a bit looser because the rear cylinder runs hotter and expands more than the horizontal cylinder.
-Jeff
I don't subscribe to that theory...
but whatever makes you happy.
The real truth is it isn't all that critical.
As long as you get them so they're not falling off when cold...
or bow string tight when hot...
you'll be good to go IMO.
Quote from: ducpainter on April 06, 2010, 05:11:55 PM
The real truth is it isn't all that critical.
As long as you get them so they're not falling off when cold...
or bow string tight when hot...
you'll be good to go IMO.
I agree. I think because of the damage a broken belt can cause, that there is much hand wringing over this subject. How many times have you heard of a belt actually breaking? I am sure someone has experienced it, but I cannot recall ever reading or hearing about one breaking and would bet gross maladjustment or extremely excessive mileage was a factor.
-Jeff
Quote from: jgrm1 on April 06, 2010, 06:37:26 PM
I agree. I think because of the damage a broken belt can cause, that there is much hand wringing over this subject. How many times have you heard of a belt actually breaking? I am sure someone has experienced it, but I cannot recall ever reading or hearing about one breaking and would bet gross maladjustment or extremely excessive mileage was a factor.
-Jeff
I've seen one broken belt, but a bunch that were really close.
The most common cause is a failed tensioner or idler pulley bearing.
I've gone back and forth with members who thought that belt tension is absolutely critical. I also subscribe to not too loose when cold and not too tight when hot ~3-4mm seems to work. Were the 900 motors 5mm? I believe the DS need to be just a bit tighter.
i usually move the tensioner in using my thumb on one roller and fingers on the other until all the clearance is gone, add a touch of preload and tighten the bolts. the 1000 has no movement of the belt off the rollers due to the positioning of the rollers, but the smaller motors allow the few mm movement at this. just my method.
I definitely noticed my bike ran better after replacing the belts. I attribute this to tighter belts. After 12,000 miles the belts were a little loose.
What works for me is I put the crank at TDC, lock the cams in place with some bolts machined down on the end that fits in a notch on opposite end of cams. When the bolts are in the notches, the timing mark on the pulley will be pointing at the mark on the engine. Loosen the cam rollers, the rollers will move when tension is put on the belt but the cam will remain in time. Then I place some folded chipboard approx 4 mil thick between the belt and the tensioner. I get it about as tight I can, tighten everything up and remove the chipboard. If it too tight or too loose you can just add or subtract a fold of chipboard and try again. When you get it like you want it, it is easy to repeat and get close to same tension every time. So far, so good.
hello everyone,
Just bought my 2008 s2r1000 and luv it.
just want to comment on the vertical cylinder running hotter than the front one. I don't believe that for one minute.
I just took a quick look at the engine and you can clearly see that the vertical cylinder has much more cooling capacity(fin surface area) than the front. Its important for both cylinder heads to be close in temp(whether high or low) so they are both equally efficient.
cheers