I am having same problem with a new FOX 3.2 i wil try and lean low end up as suggested i did that once today but it would hestitate until warmed up so i thought it was to lean so i richen it up some. I noticed that after warmed up the low end was fine. Thanks Bruce going to mix some fresh Amoil 2000 up 64/1 to i am using lawn boy right now for break end 40/1 i think it is to rich. I looked at the plug and it wasnt to bad but was not the nice tannish color it was dark .