I have been helping my neighbor by replacing the piston on his ms251 that he ran with the wrong fuel oil mix. I ordered a piston from Baileys which took 2 months to finally get here. I was just installing it into the cylinder and following the service manual to the T. Everything oiled and aligned. I applied maybe 5 lbs of pressure to seat it into the cylinder and ping. The top ring is now 2 pieces. I have already spent way too much time on this saw and really dont feel like waiting on a ring to come in the mail. I am hoping you guys will say "put her in as is, it will be fine". But I get the feeling the response it going to be "order another ring". Also can anyone offer advice as to how to avoid this in the future, the ring seemed super fragile.