I have a 3 year old HRR21610VKC which suddenly has a hard to pull start cord. It fired up and then ran pretty good other than maybe a little rich. I shut it down and then it started with an easy pull but ran poorly for a few seconds before cleaning out and rev up ok. Then I shut it off again and it was hard to pull again after a short break. I pulled the spark plug assuming gas was somehow hydrolocking the piston but it seemed ok but with a very sooty plug. Not sure where to look next, Thx in advance!