Valve Adjustment

While this page is nested in the 2V side of my website (the 900 came first), the same principles apply to both the 2V and 4V valve adjustments.

Here's some information to help the beginning Ducati mechanic relate to some theory about adjusting the valves on our eccentric machines. If you're not a mechanic, then maybe you'll appreciate what your mechanic goes through in determining how to adjust your valves.

Also see the desmo page for a better picture of the valve gear.
  • Make sure that the cylinder that you're adjusting valves on is at TDC.

  • Measure the unloaded and loaded gaps. Please recheck your work once you're done with a cylinder... rotate the engine and simply double check.

  • In my notes for installing MBP collets are pics of the valve gear during a valve adjustment. The steps shown there are identical to this valve adjustment.

  • The difference we'll call delta (D). This difference is also the closer shim clearance.

  • Now you subtract 0.02mm from D to figure out how much thicker the new closer shim should be, which I'll call dc, for delta close.

  • The next step is to figure out the adjustment for the opener shim. The unloaded gap is the opening clearance... now you want to subtract .076mm (.003") or .10mm (.004") to figure out how much thicker the new opener shim should be. Let this quantity be do, for delta opener.

  • Remove the shims that you need to adjust, measure them, then get new ones to replace them.

A real life example:

Intake Valve.
Desired clearances: opener = .003" = .075mm, closer = .02mm (unmeasurable in inches).
Unloaded gap = .004" = .101mm
Loaded gap = .006" = .152mm

D (delta) = .152mm - .101mm = .051mm
This is the clearance under the closing shim.

dc = .051mm - .02mm = .031mm
This is the difference in closing shim sizes we will seek.
Pay attention to "direction" as we want a closing shim that's
.031mm thicker.

Opener gap = Unloaded gap = .004" = .101mm
do = .101 - .075 = .026

Remove shims then measure with micrometer:
Closing shim = 6.52mm
Opening shim = 3.45mm

New Closing shim = 6.52mm + dc = 6.52mm + .031mm = 6.551mm or 6.55mm
New Opening shim = 3.45mm + do = 3.45mm + .026mm = 3.476mm or 3.47~3.48mm

Some Notes:

Now, see I use a piece of cylinder stock to help me check the shim size. I put the 3/8" x 3/8" roller bearing piece in on top of where the valve's rings sit, then measure the total clearance, then subtract the height of the stock when doing the calculations. Of course, this always adds some confusion, but that's part of the mystery in desmo valves. People with 4V motors will want to run down and buy a Kawasaki small valve shim for their stock, and get a 3.00 mm one to make the measurements easier. The 4V motors have different diameter (smaller) valves than the 2V motors.