Some more info will help us help you. What year, make and model of sled are we tinkering with?
Looks like a lean condition burn down. Bad fuel, crank seal failure, carb boot cracked and sucking air are a few possibilities. It's not the end of the world. Is the jug OK or did it get scored? If the jug is OK replace ALL the gaskets and seals while you have it apart and throw a set of SPI pistons in it and call it good. Go through your carb(s) and check those boots, replace if questionable.
DON'T just throw a piston at it....you will be right back here the first ride.