I remember from a previous incarnation of this forum a thread about Accucraft burners and the reason why the flame is all the way into the smokebox. The story so far is that my Mortimer was running fine till one day it just stopped with no gas coming into the burner. I removed the pipe that connects the gas tank and the burner, took the jet off and there was a large ball of PTFE tape in the jet tube. That is now removed and the whole thing put back together exactly as before. The only problem is that the flame now sits right at the front of the boiler / in the firebox. When you light it there is no pop and the flame doesn't seem to want to go back up the boiler / burner tube like it used to. If you increase the gas flow the flame shoots out the front, as high as the top of the funnel (that gets your attention!!! The hairs on my hand will grow back one day soon!!) This was covered in the other forum in some detail, but I can't remember what the cause was or what the solution was. If someone can remember I would be very grateful, as I am sure it was something relatively simple to sort. Many thanks.