there is a "thing/cover/whatever" wrapped around the valve springs. This broke on one cylinder. See picture. Found a picture on the web which shows it new. My questions are:

- whats that thing called
- What is it doing, is it necessary
- easiest way to replace. Heads off?
- common problem?

( I know I have to search for the small parts in the engine. Hope I find them in the sump. Cross your fingers..... )