Like the 2 Valve application, All the 4 valve engine powerplants continue the use of hardened steel half-ring.
Unlike the older technology, Ducati have moved to a full radius seating area in the return shim. Although this should be an improvement, the half ring clearance to the closing shim is excessive - leading to an absolute minimum of contact between the half ring and the closing shim seating area. Further, the half rings frequently have manufacturing burrs that prevent correct seating and are in many cases distorted.
The net result is that the half ring walks around between the valve stem groove and the return shim. Frequent valve adjustment (See Technical Specs), broken valve half rings - and under extreme conditions - broken valves are common effects from this design.
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