Davy wrote:
Theo,
the symptoms suggest a partially blocked carburettor main jet. Enough fuel
getting through for idling but not enough for full power.

Thanks. Whereabouts would I find the carburettor - just follow the fuel
line? Is that where the throttle cable goes (which incidentally at the
moment only really has two positions, start/on and a tiny bit further down
splutter/die). Or should I take the flywheel assembly apart? I don't have
any documentation, so I don't know where things are likely to be.

The spark plug and air filter were pretty filthy, so I wouldn't be surprised
if there were things blocked inside.

Theo