I bought a 2002 KAwasaki 900 STS. When I put it in the water, it would not go over 12 mph. A friend of mine is a mechanic and he took the top end off and found the back piston skirt shattered. He honed out the cylinder and replaced the piston and rings. I took it out on the water and it ran fine topping out at 42 mph. I used it for about two hours that day. I had enough oil and fuel but the low oil indicator started blinking indicating it had no oil, but it did. I brought it back to shore, shut it off and checked the oil. There was plenty. I started it up again and it went back to only going 12 mph. My friend took it apart again and found the same back piston skirt was shattered again. What could be causing this?

 

if the block is egg shaped i would have the block check out be a machine shop