Hi,

Welcome to the world of fault finding. In order I would:

Check the glow plug.
Check the fuel lines for splits.
Check for air leaks around the carby.
Check the INTERNAL PLUMBING of the tank, clunk position etc.
Check for internal motor problems, bearings, back plate seal etc.

In short if it has fuel to the carby and the plug glows it will at least fire.

Happy fault finding,

Colin