Ducati Valves Question

[marc11]

Does anyone know if Ducati valves tend to tighten or loosen over time?  I know most bikes the valves tighten up at first as they stretch a bit, but I recall reading in more than one place that Ducati valves come out of spec mostly from the colletts (sp) being squashed/cracked/etc which would make me thing they loosen up over time.

Anyone know?

[Sock Puppet]

I've never had a loose valve on my Ducs, they have always tightened up. This is why you will read about many owners who are able to "sand-down" the shims to bring them into spec.

[jed]

I've got a good 'tick' coming from the rear cylinder.  Any chance that could be a loose valve?  It's about due for the 12k service so I'll find out in any case.

[Desmo Demon]

I've had valves get "looser" and "tighter".....
 
Basically what happens is that, as the valve seats more into the head, the closing shim clearance becomes bigger. On the other side of things, the opening shim clearance becomes smaller (as the valve raises into the head). These two are actually a bit more independant of each other because of clearances and wear, but too much change on one can effect the other. It is often said to check the closing shim clearance before doing the opener, because of the relationship that they have with each other.
 
I have heard where a closing shim allows too much clearance and/or the opening shim has negative clearance (always is pushing the valve open) and the valve never fully seats. This results in burning up your valve.
 
On Desmoquattro engines, smaller clearances can help in reducing the chance of flaking chrome on the rockers. The larger the clearance of the valves, the more impact the pieces see, the more chance of damaging the chrome on the rocker....and other internal components......There have also been some reports of flaking chrome on 2V and Testastretta engines, but they are quite rare.
 
BTW, With my 748, I had to change 13 of 16 shims and replace four rockers for flaking chrome. With my ST2, there were three valves out at 6k, one opener out at 12k miles, I skipped the 18k service, and at 24k (this past weekend), I had two closers that were out.

[st ryder]

IIRC, Ducati's latest promo/literature mentions hardened valve seats, (made from beriliyum?) re the new '07 and on increased mileage service intervals, ie less wear/recession as the valve closes against it, therefore shim clearances stay in spec longer.
 
Those are good Ducati shimming pointers re doing the closers first, and the relationship between the desmo's moving parts/valve train, thanks.
 
Am I safe to assume the old adage about shimming exhaust clearances on the loose side of specs, and intakes to the tight side of clearance specs holds true for Ducatis?
 
Regards,
 
Frank
2005 ST3 (Red!)
Vini, Vedi,...Ducati!
 
(BTW, I've heard ST3 rockers on at least 1 bike, have shown *possible* rocker fkaking, like desmo4's and the TS')
 
 

I've had valves get "looser" and "tighter".....
 
Basically what happens is that, as the valve seats more into the head, the closing shim clearance becomes bigger. On the other side of things, the opening shim clearance becomes smaller (as the valve raises into the head). These two are actually a bit more independant of each other because of clearances and wear, but too much change on one can effect the other. It is often said to check the closing shim clearance before doing the opener, because of the relationship that they have with each other.
 
I have heard where a closing shim allows too much clearance and/or the opening shim has negative clearance (always is pushing the valve open) and the valve never fully seats. This results in burning up your valve.
 
On Desmoquattro engines, smaller clearances can help in reducing the chance of flaking chrome on the rockers. The larger the clearance of the valves, the more impact the pieces see, the more chance of damaging the chrome on the rocker....and other internal components......There have also been some reports of flaking chrome on 2V and Testastretta engines, but they are quite rare.
 
BTW, With my 748, I had to change 13 of 16 shims and replace four rockers for flaking chrome. With my ST2, there were three valves out at 6k, one opener out at 12k miles, I skipped the 18k service, and at 24k (this past weekend), I had two closers that were out.

[Desmo Demon]

Am I safe to assume the old adage about shimming exhaust clearances on the loose side of specs, and intakes to the tight side of clearance specs holds true for Ducatis?

For street riding, this is one of the more common thoughts. I typically try to stay on the larger half of manufacturers recommendations for the closer shims and stay within the recommended range for the openers. I have changed a few openers that were right on the edge of the high side, though. The openers are the easiest to change out, I like to run them a little tighter (lowest end of the recommended specs). If not for any other reason than to limit the abuse they take. I'm hoping that by running closer opener clearances on the 748, I won't have to change out my rockers for flaking chrome as often.....I'm planning on eventually changing all the rockers to Megacycled ones, eventually.