The ,engine is an 11.5 Tecumseh Enduro XL/C Overhead valve, the model no is 13A1458B600 and the other serial no on the label is AJ292L10012. I am not certain of the age of the unit but I believe it is about 10 years old but has had very little use so appears much newer. I have cleaned the carb.
Have carried out the spark test as you suggested and the spark appears strong.
Previously I drained the fuel tank via the pipe to the fuel filter put in a new fuel filter drained and cleaned the carb and refilled the tank with fresh fuel. I have checked again today and there is no debris in the tank.
The route of the fuel line seems ok and would not appear to be too close to any surface that gets hot.