Chainsaw Repair

 Had it running after carb rebuild. Was getting ready to stick it in some wood with 28". Backfired and all she wrote. Being the complaint was broken ring by past owner. I went to pulling muffler. Yep broken ring. Last time I figured the guy had ran the crap ring that came with the afm lrb piston. This time it was a new caber ring. So to figure out if it is the cylinder ext port or the lrb piston.