yes tappet face wear is very very common on these...

and then when you adjust them using a feeler gauge you are still left with a large gap in the middle, which is where it counts.

to do the timing chain is easy, the plastic tensioners can wear out, and the chain becomes slack. eventually the chain will then wear through the casing. to replace the tensioner you have to drop the sunp

ive done lots on these engines and when set up correctly they are very very quiet...its just that people tend to skip parts on the servicing, and the top end suffers badly then