Hi Martin
the plug is bad , the pump doesn't have a mark , that was on the older model , mine is a 1980 model which you can only set the gap on, not line up the pulley.
i was speaking to another guy today and he is certain it's the baffel which i think has never been cleaned. I'm going to clean it tonight and see if that make any difference.
i will update once i have tried it.
thanks
brad