It is the B234 that is an interferance engine. All the other B1x, B2x, and B2x0 engine are supposed to be safe from timing belt/chain breaks. The later model engine belt (post '85?) is simpler to change due to a change in the way the pullies are mounted, but they are all supposedly simple to do. After 1000km or 600mi, loosen the nut on the belt tentioner through the plastic plug on the cover, and tighten again. This is to get the tention right. I suppose that if you are going to run with the belt past it's due date, just do a re-tention to make sure it is still tight.