hiya, i also have a champion lawnmower which once left standing for a while it wont start, the answer is if you remove the top cover(3 13mm nuts) and clean the rust layer off the flywheel then replace the cover then remove and clean the spark plug. depending on how long its been standing their is two nuts on the bottom of the carburetter remove the one thats at an angle its a 10mm spanner and drain the fuel out replace it and put some fresh fuel in, then put the rev lever onto choke position pull the brake handle up(the one on the handle bar) and pull the cord and it will start their is nothing complex about the engine as long as the fuel is good and the spark is ok it will definatly fire up. Good luck and happy mowing
chris, May 2008