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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.
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.
