What causes a 17.5 Briggs and straton to backfire and not start?

A 17.5 Briggs and Stratton engine may backfire and fail to start due to several issues, such as incorrect ignition timing, a faulty spark plug, or stale fuel. Additionally, a clogged carburetor can prevent the proper air-fuel mixture from entering the engine, leading to backfiring. Other potential causes include a damaged exhaust valve or air leaks in the intake system. Regular maintenance and checks can help identify and resolve these issues.