Thankyou! The problem wasn't in the valves, the jet ski was turned upside down in the water and when you want to roll it back you should do it clockwise but they didn't counter clockwise and the water got through the intake inside the cylinder, and they starter it with water in the cylinder and water can't be compressed like air and damaged the piston rod!
They don't have weak points, very good engines! Valve adjustment on time and you are good to go! Mine was turned upside down and someone tried to start it with water inside the cylinder and broke the piston rod in pieces!
