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Ducati 4 Valve Belt Replacement

 Ducati 4 Valve Engine Belt Replacement

Changing the cam belts on your 4 valve Ducati is a straight forward procedure and one that should be done at the required intervals. Belt tension should be checked when other services are done to ensure the belt tension has not significantly changed.  Belts are inexpensive compared to replacing the valve train: replace the belts as required in the maintenance manual.

Specialty Tools Required:

  Harmonic Belt Tool
  Engine Turning Tool
   Cam Holding Tool

There is a necessary amount of dis-assembly that may be required. Removal of fairing, radiator, and various other interference pieces may be required to access the cam belts.

   

Loosen and remove the bolts securing the cam belt covers.

Note: on some models removing the oil pressure sensor facilitates cam belt cover removal:
Clean the area around the oil pressure sensor.Remove the oil pressure sensor using a 22mm socket or a crescent wrench (removing the sensor makes removing the cam belt covers much easier).

Remove the cam belt covers.

REMOVE THE SPARK PLUGS

  Remove the cover plate form the alternator cover.   Install the engine turning tool. Gently tighten the engine turning tool securing bolt.

When looking at the engine from the left side, the engine rotation is counterclockwise. Verify the motorcycle is in neutral and

THE SPARK PLUGS ARE REMOVED

     
 Vertical Cylinder
 Cam Drive Gear
 Horizontal Cylinder

Using the engine turning tool, rotate the engine counterclockwise until all timing marks line up. Typically one cylinder will be at Top Dead Center when the timing marks align. The timing marks are on the cam belt gears and on the engine case. (lay shaft cam belt driving gear).

  Once the timing marks are aligned correctly, install the cam wheel holding tool on the vertical cylinder.
Pictured is the vertical cylinder of an ST4 with the cam wheel holding tool installed. This will hold the cam gear in place while the belts are replaced.

   Loosen the cam belt tensioning nuts holding the eccentric rollers in place. Remove the nuts completely and set aside. Slide the eccentric rollers off their mounts. Do not lose the spring washers located between the eccentric rollers and the cylinder head casing

 

Remove the belts. Begin with the horizontal cylinder and slide/work/wiggle the belt off the cam gear first, then the lay shaft. After the belt is removed from the horizontal cylinder, remove the belt from the vertical cylinder.

Inspect the tensioning roller and the intermediate roller for wear. Use your fingers and spin the rollers. Check for play and or smoothness in the rolling motion. If there is more than a nominal amount of play, replacement is necessary. If the rolling action isn't smooth, it is time to replace. Check to verify the mounting studs have not backed out of the head. Inspect the belts for wear and/or fraying: excessive wear and fraying can indicate faulty/stuck rollers.

Clean the rollers and the areas around the gears.

BELT INSTALLATION

If you are checking the valve clearances and have made all the adjustments/replacements necessary, the valve train can now be reassembled.

Once the bearings, gears and surrounding areas have been cleaned and inspected, it is time to install new (or old if they have few miles) belts.

The cam gears may have been moved during the valve servicing. Align the cam gears to the correct marks and install (or reinstall) the cam gear holding tool. Verify the gears are still in alignment with the timing marks on the engine. Cam gears can move during the belt removal process.

 

  Slide the new belt onto the crank gear. Making sure the timing marks stay aligned, slide the belt onto the cam gear for the vertical cylinder. It is a snug fit and may take some patience to get the belt on. DO NOT use a screwdriver or other sharp tool to coax the belt onto the gear.

Slide the belt so it is fully seated on the cam and crank gears.

Install the belt on the horizontal cylinder.


  Here is the engine with both belts installed awaiting tensioning: Properly tensioned belts give the best assurance of long life and proper performance for your engine. The best way to know for certain the tension is correct is to use the cam belt tensioning tool. It is an electronic tool that measures the frequency emitted by a belt under tension (much like a guitar string).
 

 Start with the vertical cylinder. Apply tension on the belt using the tensioning pully and tighten one of the tensioning pully retaining bolts. Place the probe end of the meter near the flat (outside) side of the belt and using a thumb or forefinger "Pluck" or "strum" the belt. The belt will vibrate and the meter will briefly display the reading.

Setting the belt tension:

 
   
Meter is ready for input
The Meter has received an out of range input ("strum") and the belt must be tightened or loosened: gently loosen the retaining bolt and apply more/less tension to the belt and check again
A properly tensioned belt will display 110 (+ or - 5) on the meter.

 

  Once the vertical cylinder is properly tensioned, repeat the tensioning process for the horizontal cylinder. When both belts are tensioned correctly, use the engine rotating tool to rotate the engine through several revolutions. Align the timing marks and check belt tension again. 

  When the belt tension is complete, reassemble the covers, oil pressure sensor and sensor lead. Install the spark plugs and spark plug leads. remove the engine rotating tool. Inspect the cover plate o-ring looking for nicks, cracks, or cuts. If defective replace the o-ring. Reinstall the cover plate and snug the bolts.

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