it could be that it is caused by the piston fit in the bores being too loose and getting piston slap where the piston slaps up agians tthe inside of the bore. if i were you i would junk it and buy a second hand one for about $300 if the piston to bore clearance is to great if you wanted it to run properly again it would need to bored oversize and oversize pistons and rings fitted.
the part you are talking about that has broken off is the piston skirt.