Gents
I fitted the new plugs and took her a spin this morning (flying jacket on as it was spitting and I really cant be fagged putting the roof up for a short spin). She actually performed very well and I think acceleration was crisper than normal (that or the double espresso was kicking in). When I got her good and hot and turned the ignition off she still over-ran (dieseling as has been pointed out). But is was a lot less than normal.
I then eventually managed to get the nut slacked on the distributor slackened off (special 9.5 nut with rounded shoulders and a shallow screwdriver proof slot). I adjusted the timing back a couple of degrees according to my ebay timing light. She looks like she is at about 14 degrees at 900rpm. This is a few degrees less advanced than she was before. She sounds healthy and when I turned her off she stopped very nicely. There was the briefest of scuttle shakes and then peace and quiet.
I did this a few times and the same resulted each time.
I have suffered this symptom through a 3000 miles trip round the Alps and several thousand other miles so I don't think it was a real problem. But hopefully backing the timing off will ease the situation and put less stress on the engine and starting as a whole. But I will get her timed professionally soon.
Many thanks to all those who gave very useful advice. I have used forums before and especially in the Triumph bike world there are some very overbearing characters. I have not found here. The sort who WRITE IN CAPITALS as if they are shouting and the sort who criticise you for being naive or inexperienced. So thanks.
And finally may I recomend Robin Hood motor factors in Chelsfield in North Kent. Very old school and had my plugs in an hour and charged me £10 for the set. I will try the BR7ESs for a while and see how they cope before resorting back to the BR6ESs.
