Thank you for responding
I'm not sure it can be rings because the engine was rebuilt by previous owner only a few thousand miles ago and with rings I would have thought it wouldn't happen suddenly?
I did think valve guides as they may have gone hard due to the engine not being used.
To be honest I haven't let it get warm as I shut it down because of my concern over the smoke. I think I might remove the plugs and see what they look like, see if any of them are particularly oily. I might then run it up to normal operating temperature to see what happens.
Thanks again for responding
