Fixed the float level problem on mu speed demon 650 & after I adjusted the level to the middle I figured the stumble I had prior to this would be gone. Still there. I have adjusted the mixture screws as well & can't rid of the stumble. It starts right at take off & stays with me even on the freeway. I assume it's lean, but what else can I do? I ried advancing the timing, but that doesn't work either. The problem started a couple of days after I retarded the timing b/c the engine sputtered after I shut it off, so I figured it was running rich. Out of ideas.