Oh GOODY, a practically new engine!
Wait a minute.. the guy was told
by the previous owner that the engine was replaced due to running without oil, and he's passing that along as firsthand knowledge? So for it to be true, there would have to be two non-lying parties in a row, each of whom would benefit greatly by lying.
Sounds like a hell of an advantage for negotiation.. I wouldn't pay anywhere NEAR 4k for that bike, especially after your research with the DMV uncovers that the bike
must have been wrecked, as verslagen1 indicates.
You don't have to call him a liar.. even though presenting hearsay as fact is bordering on lying.. just point out that he got hosed by the previous owner.
Also, be sure that you really want to keep the bike a long time.. run it to dust and/or part it out when you're done, because you won't get squat on resale.