I know there is a difference in an "A" and "B" piston and cylinder but can a used one be used in the other without any harm?I have an A c&p and some one gave me a used "B" piston. Will it work without tearing anything up? This is in an older 266XP that I will be using maybe 15 to 20 hours a year. I know they don't cost that much, but the wife got laid off Friday .I now have to watch my spending a little closer This is the first saw I have ever tried this on as I am a complete newbie at this. I did do a pressure and vacuum test and that all came out good. but I did that without the piston in it.:newbie:I hope I am not being a nuisance by asking all these dumb:newbie: questions. I appreciate all the help in the past !! Thanks