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ducati desmodromic valve system belt driven cogwheel ball bearing closing lobe opening lobe camshaft opening rocker valve stem closing rocker valve seat valve camshaft reverse lift closing lift opening reverse lift closing lift opening camshaft note narrow width opening lobe closing lobe these two rockers are on the same rocker shaft drawn separately for illustration camshaft closing rocker valve stem opening rocker the ducati desmodromic valve system is somewhat difficult to illustrate in 2-d so please forgive the poor illustrations basically instead of using a spring to close the valves and additional cam lobe is used to close the valve the opening cam lobe pushes on the opening rocker which opens the valve the closing cam lobe which is on the same camshaft pushes on the closing rocker as soon as the opening lobe starts receding stops lifting thus no valve spring is needed to close the valve however a small spring not shown exerts force on the closing rocker so that when the valve is closed it seals against the valve seat ensuring that the combustion chamber is sealed there are several different configurations layouts of the desmodromic valve system that have been developed by Ducati over the years through research and development the system shown above has seen wide use on several models the system to the left is used on newer models desmoquattro quatrovalvole 4 valve systems it is more compact using only one rocker shaft and it allows for a narrower included valve angle also the lobes on ducati camshafts can be narrower because they don't have to overcome the force of large valve springs used on regular over head valve engines