I have one! Mine is in ??? condition - may never run again - LOL! It was given to me.
If it's a 4000 it has a 90cc 2-stroke motor. If it's blown, you'll have to either replace it with like motor or redo the entire rear end to accomodate the mounts for a regular 4 stroke motor. You will have to cut and weld as to make a place for the new engine to mount - it WILL NOT be a take out put in process.
It could be a really nice cart, but I think you could add a little $$ to the $150 and have something usable up front without much of a problem. Be patient!