250 exc sand dunes stutter

I took my 01 250 exc to the sand dunes this weekend just to try it out. It did pretty good but I noticed a chunka chunka chunka type of feeling on take off. Kind of like a stuutering at low rpms. Once I got the RPM's up it stopped but it was always there on takeoff. I'm a fairly experienced rider but this three second rattle or stutter is new to me. Any thoughts?

A buddy of mine told me today that it was probably caused by the paddle tire hoooking up and then spinning to the next paddle making the chain go tight and loose cuasing it to slap against the swingarm. This sounds possible. What do all think?