Just got a blaster on trade n guy gave me a top end n piston with it..put the top end on and it fired up for a few seconds then stopped ..crank it back up it had a pingin sound so i took top end back off inspected piston put top end back on then it wouldnt fire up seemed like it didnt have enough compression it read 60 psi..so i took top end off again and now the piston acts like it doesn't want to fit it goes in top end but its hard to go up n down now seems like it got to big but i didnt do anything different when taking top end off or drop piston..piston still looks new