almost definitely a reed valve, if it does not seal it will blow backwards through the carb
BR8ES is the wrong plug book says BR9EYA I had trouble finding them I got them at NAPA auto parts. I burned a hole in side of piston while using BR8ESI had already ordered reeds before the post. Just wanted someone else to confirm my diagnosis. That was definitely the problem, one of the tabs was blown back into the cage... no pieces missing... hopefully no cylinder damage. Thanks for the advice. Ski runs better, although new plugs seem to burn rich (dark brown to black)... BR8ES, does anyone know what the gap should be set at? Also, does anyone know what the procedure is for adjusting the carbs?