I think I figured it out.

http://www.peachparts.com/shopforum/tech-help/161055-sears-multimeter-82139-duty-cycle-check.html

I am also using a sears meter. I swapped the leads (red in pin 2, black in pin 3). Now I get 47% at idle and 52% at 2500 rpm. Although the readings are a little wild at 2500 rpm. It can go as low as 47% and as high as 55%.