s1 going pop

Hi all, just got my s1 mot"d and back on the road after twenty years sitting around with various owners. all seems well apart from a noisy rear diff, the other, strange thing is that when i switch off then a few seconds later the exhaust pops and blows a smoke ring, very amusing but not right. any one else had this?

could do with a decoke

If its not had much use for years I'd use it for a bit and see if things improve -or get worse. It sounds like a an attempt to run - on due to something glowing in the combustion chamber and the build up of soot may burn away. It could be a valve on the way out, wrong or dirty plugs . .

Worth checking the timing.

If its regular and consistent you could develop the trick of turning it off, getting out and kicking a tyre whereupon it blows a smoke ring!

Your names not uncle buck is it?

http://http://www.youtube.com/watch?v=lPqPDdiiJIw&feature=youtube_gdata_player

uncle bucks happens while running, on mine its after i switch off. as to a decoke, its just had one, and a new valve seat, i suppose the exhaust tappet clearance could have closed up as it all settled in, would that cause this?

is the mechanism in the distributor stuck so it is not advancing and retarding properly, side valve exhausts can be a bit poppy on the overrun.

Hi you may have a leaky carb ! Maybe gasket or float needle letting fuel thru until pressure drops a bit ! Does it start up a bit rich or slow starting ? If so wet plugs may be a symptom of a fuel leak into the manifold! Also something must be igniting the extra fuel after stopping the engine ??? If there's no carbon then somehow you have enough heat to ignite the extra fuel ! Does it do it after just a short run ?( engine not hot ) if not then it may be running an advanced timing !! Dizzy fault maybe !