"It should be remembered that on Desmodromic valve timing systems any increase in opening clearances will automatically decrease the closing clearances and vice versa.
If you change the opening adjuster you must therefore also change the closing adjuster."
I do not understand how the one can effect the other.
They are opened and closed by different cams. When you check the opening clearance the valve is always going to be closed unless you have less than no closer clearance.
Surely if I reduce the opening clearance with a larger shim it wont effect the clearance clearance between closer rockker and closer cam lobe.
If anyone could shed any light on this issue I would be grateful.
I dont want to put it all back together and then read somewhere that I have done it wrong.
For any given valve (either intake or exhaust), even though they are opened/closed by different cams and different rocker arms, the shims are on the same valve stem. So putting a thicker opening shim (at the top of the valve stem) pushes the whole valve stem
downward. This will reduce the clearance on the closing shim (mounted part of the way down the valve stem) by the difference between the thickness of the old opening shim and the new opening shim. If the closing clearance was correct before changing the opening shim, it will now be wrong. The fact that they are actuated by different cams and different rocker arms is immaterial.
In practice, you should start by measuring the closing shim
clearance, and adjusting that to the correct value (I use zero, which is tricky to achieve, check out the Pro Italia video, the Ducatitech.com video, or LT Snyder's 2V maintenance manual for more details). Then replace the opening shim to compensate for the closing shim change and
the original error (if any) in the opener clearance (I use 0.1mm as my target here).
It sounds complicated but really isn't, if you're careful and think about the mechanical design of the valvetrain!