Thanks for the responses, I thought that the tensioner worked off the oil pressure to tension the chain, i.e. thats the symptom produced upon start up when you hear the slight rattle until the oil pressure comes up. Mine just started this but has subsiquently stopped, now i've notice the erratic oil pressure. It may just be a coencidence<sp>. The oil pressure at idle drops to 0 but will imediatly jump, it only runs at 3 bar at highway rpm, is that normal?
thnaks again for the help, this is the most useful site i have come across on the net.