I have a Wolf 800w generator, looks the same except for the colours/branding. It was an absolute pig to start and would run for a while before cutting out and again taking ages to get restarted. So much so that the recoil starter rope broke on me.
Aaaaaaaanyhow, I eventually replaced the spark plug (can't remember the brand but it was Chinese) with the nearest equivalent NGK (managed to find the equivalent Champion but couldn't get one and ended up with NGK but that's by the by). Don't know why that took me so long, I'm an ex-mechanic :-[ but it was a different machine from then on, starting first or second pull. Nice and quiet and reasonably economical too.
It had enough power for drills, grinders etc.
Unfortunately the abuse seems to have killed it - I think it has a fuelling problem now as it won't start at all.
I paid either £50 or £60 about 3 years ago from Screwfix for mine.
Hope that helps some.
:)