Craftsman briggs and stratton Platinum 21 HP 540cc XRD

Engine started running rough. Would die at low idle speed...a few days later if appear to have a week battery and had to charge it to start the motor...it was time to do a spring time up anyway so changed oil & filter, air filter, spark plug....Sent to restart and it would not Frank completely over again..changed out battery and still would not crank fully...plug plug and was able to crank the motor freely, checked spark, it was decent. Took cool off, cleaned minor rust off of the face and...

Craftsman briggs and stratton Platinum 21 HP 540cc XRD