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Discussion Starter #1
Just finished checking the clearances on the vertical cylinder.
Not the easiest thing, even with the head sitting on my workbench...
Opener clearances were measured without forcing the closer arms against the cam.
Closer clearances were measured with the opener rockers and shafts out, and (carefully) using a screwdriver through the opener shaft hole to pry the closer rocker into intimate contact with the cam. That's the only way I could figure out to get the closer rockers up against the cam, there's next to nothing to push on at the valve end. Maybe someone with FHE on 4-valvers can give some guidance.....

Exhaust Opener Left = .0075" ---- Spec .006" - .008" , Limit .002"
Exhaust Opener Right = .0070" ---- Spec .006" - .008" , Limit .002"

Exhaust Closer Left = .0015" ---- Spec .002" - .004" , Limit .008"
Exhaust Closer Right = .0045" ---- Spec .002" - .004" , Limit .008"

Intake Opener Left = .0055" ---- Spec .004" - .006" , Limit .002"
Intake Opener Right = .0055" ---- Spec .004" - .006" , Limit .002"

Intake Closer Left = .0060" ---- Spec .002" - .004" , Limit .008"
Intake Closer Right = .0040" ---- Spec .002" - .004" , Limit .008"

Everything looks on the loose side, except for the exhaust closer left. IIRC, tho, the "old" specs are nearly zero clearance for the closers.
I'm assuming the spec values I quoted (from my shop manual) are the "new" (looser) values. I looked a little for the "old" specs, but it's a little late in the evening....

Any relevant comments or links appreciated. I'm aware of ducatisuite.com and Chris's ducatitech.com.
 

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Nick,

First, where are you measuring the closer clearances? If you have the opener rocker out, you must be measuring between the closer rocker and its shim? I think the preferred method (and the one I used), is the one detailed by Chris K on his web site:

Measure the opening clearance first. Then force the closer rocker down, measure the clearance at that same point again, and subtract the first measurement. I realize there is precious little closer rocker to push on at the valve end, but, tough sh!t...;D. Use a dull screwdriver, or a rigid dowel, and be prepared to have it slip off the end of the rocker---repeatedly. It is not a bad idea to have a spare valve seal available...or two. It took me an hour or so of practice to develop a technique that rendered consistent readings. The process is a SOB, made worse by the fact that our heads have an exhaust-valve rocker cover opening that is much smaller than a standard 916 head. Try pointing a dial indicator in there...

The zero spec thing is for a (so called) manly 2V engine. But you're right, the older specs are tighter. The cynics (Sigma) insist this was changed only to expand the service interval (ahem...), but performance suffers. To compensate, Ducati used stronger closer springs. My new heads have corsa springs, which will make checking my valves that much less of a b!tch.

Remove the limit specs from your above chart, and your target specs are basically in line with what Bruce (BCM) recommended for my SPS cams. Jon Nichols, machinist that he is, prefers somewhat tighter clearances. I set mine to the tighter end of Bruce's numbers.

VERY good idea to measure, and catalogue, all your shims for future reference. This way you can move shims around, as needed, to make your adjustments. Even with new cams, I only needed to buy two shims, and sand one.
 

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Discussion Starter #3
Tom,

Thanks for the info. first the fender, then the safety glasses, now this. You're on a roll. You should buy a handfull of lottery tickets. You're golden! ;D

Yes, I was measuring between the closer shim and the closer rocker fork.

Agreed, having a few (like, 8, for example :( ) valve stem seals handy would be very prudent. The brass drift I was using slipped off several times on the very first valve I was trying to check, and did wound a seal. That's why I went to my method....

Strong closer springs indeed! Ducati could make 'em a wee bit stiffer and dispense with the closer lobes.... :-/

My next task was to measure my shims. Seeing as all of my clearances are on the loose side, it looks like sanding down shims may not help me much here. Unless I get lucky, I'm going to need a full set of 4 closers and 4 openers just to do the vertical head. Chances are I can swap some shims around, though. I'll see what kind of a situation I'm really in after I've done the horizontal cylinder.....

I'm thinking of a special tool to push on the closers. I'm not at all fond of a standard maintenance procedure that puts delicate parts at risk. I wonder how many 4-valvers start burning oil after a valve adjust.... :-/

Thanks again.
 

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I'd love to see either of you push open a sprung valve with your hand on a screwdriver. The difference between the Ducati closing helper spring and a non-desmo valve return spring is orders of magnitude difference.

Y'all are pushing too hard. Push only until the rocker arm stops. No more force is required. In fact, pushing as hard as you can will screw up your closing shim clearance, as you will be deforming the system. I've done it.

Back to the spring to close valve concept... have you folks ever actually seen normal valve springs? They're pretty beefy. And they're only moving the mass of the valve itself. (+ the spring retainer and "bucket") The weight of the rocker arm is considerable mass in itself and adds impressive additional requirement to the spring's requirements.

The desmo closing rocker arm tells the valve when to shut with authority. Conventional engine manufacturers are still writing and rewriting software to model valve float to ensure that the spring is strong enough to keep the valve in contact with the declining ramp of the cam lobe. This is a limiting factor in the design of modern engines. They cannot use ideal or desirable cam profiles because the spring can only do so much. This is part of why the desmoseidici can rev to something like 16,000 rpm while other motogp bikes are 14~15k.

Y'all go buy yer TL1000Ss and VStroms. Then you'll spend all your hours getting to the engine... ;) ;D

:) Chris
 

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Discussion Starter #7
I was being a bit facetious about the closer springs... ;)

Biggest problem I had with pushing on the closer was it's such a small, curved surface to push on. That combined with never having done it before....

Then again, if you do it Chris's way, you can push on the closer shim instead. Hmmm....there's that FHE coming into play again. ;D
 
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