First, thanks Cessna for the excellent tutorial. Good stuff. It looks like one of the biggest time consumers is the tear-down/put-back of all the various bits. I've had my tank off 3 times for various reasons and it's a 3-4hr job "round-trip" just to get that done!
On to my question. I had heard (read actually) that when you do Desmo valves, it's an iterative process vs. a one-time setting. What I mean is, you set the opener, then the closer, then have to go back and recheck the opener, etc. until everything is just right. I didn't see this in your tutorial, so is that not the case? It would remove a lot of anxiety, complexity, and time if not.
Again, thanks for the great write-up!
When I was doing my homework for this project I found that the older ducati's are more involved when doing the valve check & adjustment so I'm sure what you read was not referring to our newer easier to work on Testastretta engines.. Neither of my shop manuals mentioned anything about it being a iterative process.
But I wanted to get a 2nd opinion and asked a mechanic this question and below was his response.
That is a good point. In theory, the opening and closing clearances are independent of each other, since the clearance being checked is the clearance between the opening rocker arm and the opening cam and the closing rocker arm and the closing cam. The shim size does not make a difference on how the valve is setting in the head, only the amount of deflection the rocker arms are experiencing.
It is typical when measuring the clearances on the older desmoquattros and all 2-valve engines to take the reading at the same place: between the opening shim and the opening cam. The difference is depressing the closing rocker to reveal the clearance for the shim/rocker and subtracting the opening clearance to find the true closing clearance. This you see referred to as the loaded and unloaded gap in several manuals and Internet tutorials.
With the Testastretta engines no such guesswork is necessary, the opening/closing rocker-cam interfaces are easily accessible. So I remain committed to the
theory that the clearances are independent of each other.
It is a good idea to check everything before reassembly.