Just broke my weed eater out for the spring and switched out my bump head with my brush cutter blade. Once I accelerate the blade to about 1/4 to 1/2 speed the blade begins to sound like it's hitting something (which it's not). I reattached the blade multiple times, and ordered a new blade thinking there was a possibility it was damaged and off balance. Still getting the same problem. It seems to operate all right at full rpm, but I'm positive it wasn't doing this when I used it last year and am skeptical to use the brush cutter now. Any help is appreciated.