A friend's son out oil in the gas tank and tried to start the thing. The gas system has been flushed and everything else done to correct the problem. Now the recoil starter is hard to pull but once I get past that spot it will move until it seems to hit that spot again and then will jerk the rope back sometimes. When I use the electric start it hits a spot where it strains to move but when it gets past that point it will turn the motor over fine and will start the motor which wil run fine. I am about to take the motor apart but does anyone have any idea what the problem could be? Bent crankshaft or something else?