There could be a possibility of a few things that could be wrong. One idea is to take the spark plug out and try and pull on the cord, if it is turning over with the plug out, you probably have oil in the cylinder. With the plug out, keep pulling on the cord a few times to push the excess oil out of the cylinder. Add some carb. cleaner to help get the oil out of the rings and change the oil after. If you pull the plug out and it is still locked, you may have ran the motor low on oil and the piston seized to the cylinder wall. If it's a push mower you have a quick solution to getting it freed up. With this, take the spark plug out and spray some WD-40 in the cylinder. Tilt the lawn mower handlbar back and with gloves grab on to the blade and rock it back and forth to try and break the seized piston off the cylinder wall. You may have to work at it for a while depending on how low the oil was. The other option is to get a wooden dowl that fits into the spark plug hole and grab a hammer and smack on it to break the hold on it. When you break the piston free, grab on to the blade in the direction that the motor runs to help clear out were it was seized. Now change the oil and make sure that this doesn't happen again. If it's the first time that it's happened, the motor for the most part should be a long runner, however if it keeps happening, your going to have to oversize the cylinder, get an oversized piston with rings, and that won't be good.
Good luck on your motor, Go Briggs and Stratton !!!!
David, July 2007
