[frans-c]

It has a single-toothed chain (solex???). Good practise would be to replace every 100k miles, although the mechanic at the dealership says that he has seen samples that've lasted over 250k miles...

You can actually feel the tension of the chain by simply removing the oil cap - that's from what I've read on other forums, haven't tried it out myself.

You should be able to deduce a lot about the chain's condition simply by listening to the motor running. I think some very minor clatter at idle is allowed, but it should go quiet as soon as you give it some gas.