piston damage

nice get it running riding weather is comin i think me and you and my nephew and whatever else we can fit on the trail we should go to gettysburgh to badazzbanshee's what ya think
 
Do you know what caused your piston to break like that? Mine is broken in the same exact way, and like yours the cylinder wall looks to be untouched. I think that my crankshaft bearings are bad and would they cause that to happen?

Thanks,
MIke
 
Mine did the same exact thing and i think mine was running lean also, but am not sure. the plug was white, and kept melting the electrodeto the rest of the plug. I have a pipe and airbox vents, so i guess a 240 main jet is too small, right?