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Title: Tech: How desmo works Post by: Spidey on June 10, 2009, 09:36:55 PM Are you one of those folks who knows that a Duc requires valve jobs and that it has a Desmo system, but doesn't know what that means? Well, here ya go. I just wanted to share. If you already know how it works, just ignore.
Below is great explantion about how valves work. Note that the author is talking about a 4 valve bike. If you click the link he provides (Here --CLICK (http://www.ducatidesmo.com/valves.htm)), there's an animation of how the desmo system works. Valves are what let the air/fuel into the cylinder and exhaust gasses out into the exhaust. Your bike has 4 valves in each cylinder head (vertical and horizontal), 2 exhaust valves and 2 intake valves. The belts turn 2 camshafts in each head, one camshaft for the intake valves, one for the exhaust valves (in each head obviously). These camshafts have lobes that move rocker arms which push the valves down into the cylinder (open) and on Ducatis a 2nd rocker arm driven off of a different cam lobe pulls the valve back up (closed). Ducati is unique in having the camshaft close the valves, almost every automotive/motorcycle engine in the world uses springs to close the valves. Keep in mind all this movement is happening VERY VERY FAST. The gap between the rocker arms and the cam lobes when the valves are closed is critical to keeping the engine running properly. To set this gap there are shims of different sizes positioned on the valve, the valve adjustment process is basically measuring the gap and swapping the shims as needed to achieve the appropriate gap. Obviously to do this you have to get to each cylinder head which means removing a LOT of stuff. As I mentioned Ducatis are different in that they have a rocker arm closing the valve as well, which means there is a shim for opening each valve and a shim for closing each valve. Check out this animation of a Ducati valve movement including the camshaft and rocker arm. This animation is from a 2-valve engine so it is a bit different than yours, it only has one camshaft in each head. CLICK (http://www.ducatidesmo.com/valves.htm) Labeled: (http://woody-racing.com/Ducativalve.jpg) Title: Re: Tech: How desmo works Post by: ghostrider on June 10, 2009, 10:12:34 PM Very nice [thumbsup]
Title: Re: Tech: How desmo works Post by: DanTheMan on June 10, 2009, 10:29:33 PM This should be a stickie!
Title: Re: Tech: How desmo works Post by: Desmostro on June 11, 2009, 12:21:56 PM sticky
Title: Re: Tech: How desmo works Post by: brains_us on June 12, 2009, 01:53:41 PM Good stuff. Good to know thats how my baby ROLLS. I feel so much more cooler 8) knowing only over ducati's do that..
Title: Re: Tech: How desmo works Post by: Drunken Monkey on June 14, 2009, 06:59:31 PM Want me to move this to the FAQ section?
Title: Re: Tech: How desmo works Post by: Spidey on June 15, 2009, 08:49:29 AM Nah, that's ok, DM. I'll do a more FAQish write-up and do a separate post. Thanks though.
Edit: done. http://ducatimonsterforum.org/index.php?topic=25350.0 (http://ducatimonsterforum.org/index.php?topic=25350.0) Not my best work, but it'll suffice for now. |