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At my first belt check at 1200 miles, my rear belt was floppy loose. After doing some research on the various methods for adjusting belt tension and reviewing the service manual, I came across several methods for adjusting belt tension. The first two are "quick and dirty methods." Not necessarily correct but will do in a pinch. The third method is the technically correct way and it preserves cam timing for those that are real picky.

1. This first method utilizes a 5mm allen wrench that is used to measure/adjust belt tension against the fixed idler roller. This is a carryover from the earlier versions of the aircooled twin. While some continue to use this method on the current twin spark engine, it is said to be not as accurate due to the assymetrical location of the idler roller and the tighter belt spec set for the twin spark engines.

2. 45 degree twist method. Adjust the belt so it twists no more than 45 degrees on the longest run. This method seems particularly inaccurate since there is no easy way to measure a 45 degree twist other than eyeballing it. Also the amount of force you use to twist the belt is going to be variable. With that said, this is the method I used for my first belt adjustment.

If you adjust your belt tension using 1 or 2 above, you are altering your valve timing slightly. This happens because the cam pulley is moving while the crank stays in TDC when you tighten (or loosen) the adjustment pulley. The amount of change however is probably insignificant so I wouldn't loose any sleep over it.

Method 3 uses a harmonic adjustment as outlined in the service manual. You can use a PC mic and a guitar tuner program on your pc for this. The factory manual spec for belt tension is 140 hz. This is the spec for belt tension for adjusting cam timing, and is not the operational tension. For a new belt, tension should be set at 110hz and for a used belt, somewhere between 70 and 100hz. Also, when adjusting belt tension, you should lock your cams in place using the Ducati special tool inserted into the cam cover on the left side of each head and loosen the cam pulley screws when adjusting belt tension. This lets the cam pulley rotate, rather than the pulley and the cam, as you tighten/adjust the belt. As an alternative to the expensive ducati tool, I use a 6mm stainless steel rod inserted into lower middle hole on the side of the cam cover. The rod locks into the locating groove machined into the side of the cam.

I've been told that the belts must be replaced every 2 years at a minimum, regardless of mileage. So, I'm almost there and plan to replace my belts this summer. I'm also going to check my belt rollers while I'm at it since I've heard of some of those going out due to bad bearings.
 

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... So, since there is no 1200 mile service check called out for the belts, I'm assuming you just decided to take a peek?
 

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Eat, sleep, play!
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Discussion Starter #3
... So, since there is no 1200 mile service check called out for the belts, I'm assuming you just decided to take a peek?
Yes, doesn't hurt to check and it takes only a few minutes.
 

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I can't beleive how much the belts in my bike loosened if they were set correctly to 140Hz at the factory. Any worse and the timing could have jumped. Its so easy to do its a no brainer. All you need to do is take off the covers and remove a plug in each cyl. You can turn the motor over by bumping ther rear wheel with the bike in sixth gear on a stand.
 

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Eat, sleep, play!
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Discussion Starter #5
I can't beleive how much the belts in my bike loosened if they were set correctly to 140Hz at the factory. Any worse and the timing could have jumped. Its so easy to do its a no brainer. All you need to do is take off the covers and remove a plug in each cyl. You can turn the motor over by bumping ther rear wheel with the bike in sixth gear on a stand.
140hz is the tension used to adjust cam timing. Operational tension is supposed to be set at 105hz to 110hz with a new belt. 140hz is too tight and can lead to premature failure of cam belt roller bearings and other bad things. Belts should be checked with the engine cold and the ambient temperature at around room temperature. Here is a partial excerpt from the service bulletin.

http://www.ducati.ms/forums/attachment.php?attachmentid=49059&d=1244183606
 

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Thanks for posting that, the table in the manual is a bit unclear in that respect. I did reset mine at 100Hz (same belts), the point was that when checked they weren't even on the radar.
 
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