Carl, only thing easy I can think of is that you're using last seasons gas and have some water from condensation or even a little rust/dirt in it. I don't know how much gas those hold, but if you don't want to chuck it outright, try running the gas through a funnel lined with an old chamois, rinse the tank with the cleaned stuff and repeat the cleaning before refilling. If thats too much of a hassle (and no old chamois), empty the tank, add a little new gas, swirl it aroung...chuck that gas and refill with the good.
If you have an old metal gas can, that may be your culprit as well.
Had it happen to me on an old lawnmower that the kids had left out through a couple of storms (still fummin and fussin over that).
Hope I haven't wasted your time with the obvious.
;-P
JD
July 2009