how do set the timing on a 3.5 hp briggs & stratton ( model # 90702 ) ?

pete, September 2006

Your Model 90702 is electronic ignition. The only way for the timing to be off is if the flywheel key has sheared.
A loose cutting blade will also cause "out of time" symptoms, as the weight of the blade is part of the flywheel action.
With the spark plug wire disconnected, check the blade for any free play.

Rick, September 2006