pete 200

2 weeks ago I bought my first Gas Gas trials bike, a 1995 250. (JT25 I think.) While playing at a river crossing my son dropped into a deep hole and sucked the engin full of water. The engine made a bad snap sound and we could see a nasty crack where the two rear cylinder hold down bolts are. The jug moved up enough to snap the spark plug off. We stripped it down right away since it was full of water. We dumped water out of the air box, carb, pipe, and cases. I had a gallon of WD40 so we filled the cases then turned the bike upside down to drain it. Is it worth fixing? Where should I look for a new piston and cylinder? Can/should I go with a big bore?