Last week steaming nicely at 55-60 with the burner on full fire continuously we had a good old bang in the burner. First time for several years so I was a bit surprised and my navigator even more so! The two tension springs which hold the bonnet (hood) down did their job although it did rise 3 inches and I had to push the smoke hood back into place.

I can't think why it did that as we had been driving for a couple of hours and as I said the burner was on full fire, the pilot in good order and a sparker going.

The only explanation I can think of is that the flame momentarily lifted due to high airflow (front air intakes on the Model H), went out, letting the combustion chamber fill with gas and then go bang. I use number 61 jets with 50/50 petrol/diesel at 120psi in a 23 inch burner. Maybe a bigger jet say 59 would give a richer mixture and be less susceptible to the extra air flow at higher speed.

Any thoughts?

Mike