what could be wrong with my honda generator?

ive been using my generator to boil my urn in my buger wagon.and now it splutters,looses power and cuts out.the filter is dirty how do i clean the filter as well.im not overloading the generator at all.as its a big powerfull generator and ive had it years and like i say,its run my urn for over a year,and i dont run anything else,just my urn.what could be the problem please