Mower start problen and questions
 

Most likely Timing is not at issue. "Timing" is rarely an issue with 4-cycle engines. In fact there are
really no timing adjustments. However there are Condensor point gaps that can be adjusted, and only after
some serious hours of operation might the "Gaps" need adjustment. Altogether Comprised within
The term-
"Spark" is your issue.
Change or clean your spark plug. A fouled spark plug would exhibit your precise condition.

Always good practice/preventative maintenance to change gas if old, using fresh clean gas and of course making
sure to keep the air filter clean ALL of time..

Hit one rock and you can have a timing issue, common on some motors, a
sheared key.