Top one is a 2009 Arrow AX9 4 stroke with a briggs and stratton racing engine.
Bottom one is a 2007 Birel chassis with a 125cc 2 stroke racing engine. it has a Mychron 4 on it as well.

I dont know very much about karts yet but am excited to learn and get these on the track asap. Any knowledge about where to buy parts, seats, tires, etc... would be great. Also if anyone knows anyone that rebuilds engines for these things contact info for future use would be awesome.