don't know how good of a dealer you have but I would expect the dealer to work with until the issue is COMPLETELY resolved. even if that means taking the second one back. the fact that both of these trimmers aren't even a week old SHOULD be in your favor. I wish I could help more because the fs70 is a great trimmer besides the plastic housing design. you have to undo the throttle assembly every time you want to remove the outer plastic shell. as I said I haven't had your issue. I use 87 octane with the grey 2 gallon mix.