Problem starting Petrol Generator?

The generator is a "Planet 2" I think company has disappeared , and I can not get to start, there is a spark, sometimes the plug is wet sometimes not, not sure how to set timing on a magneto ,changed the petrol, cleaned magnets up , it has run , its been used maybe 7-8 times,when I pull the cord to start it , it does give a sort of back fire, more like a "fut" sound, has anybody any thoughts, thank you